WAEC Mathematics 2009 past questions and answers

64 questions. Try each one, then open the answer to check yourself and read the explanation.

Question 1

Fractions, Decimals and Approximation

Simplify: (3½ + 4⅓) ÷ (5/6 − 2/3)

  1. A.1¼
  2. B.8½
  3. C.35
  4. D.47
Show the answer and explanation

Answer: D (47)

Explanation

3½ + 4⅓ = 7 5/6 = 47/6 and 5/6 − 2/3 = 1/6. 47/6 ÷ 1/6 = 47.

Open this question

Question 2

Variation

In a particular year, the exchange rate of Naira (₦) varies directly with the Dollar ($). If ₦1122 is equivalent to $8, find the Naira equivalent of $36.

  1. A.₦8976
  2. B.₦5049
  3. C.₦140.25
  4. D.₦31.17
Show the answer and explanation

Answer: B (₦5049)

Explanation

$1 = 1122 ÷ 8 = ₦140.25, so $36 = 36 × 140.25 = ₦5049.

Open this question

Question 3

Logarithms

If log 2 = x, log 3 = y and log 7 = z, find, in terms of x, y and z, the value of log(28/3).

  1. A.2x + y − z
  2. B.2x + z − y
  3. C.x + y − 2z
  4. D.x + z − y
Show the answer and explanation

Answer: B (2x + z − y)

Explanation

28/3 = 22 × 7 ÷ 3, so log(28/3) = 2 log 2 + log 7 − log 3 = 2x + z − y.

Open this question

Question 4

Number Bases

Arrange the following numbers in descending order of magnitude: 22three, 34five, 21six.

  1. A.21six, 22three, 34five
  2. B.21six, 34five, 22three
  3. C.22three, 34five, 21six
  4. D.34five, 21six, 22three
Show the answer and explanation

Answer: D (34five, 21six, 22three)

Explanation

In base ten: 22three = 8, 34five = 19 and 21six = 13. Largest to smallest: 34five, 21six, 22three.

Open this question

Question 5

Commercial Arithmetic

Find the value to which N3000.00 will amount in 5 years at 6% per annum simple interest.

  1. A.₦3,900.00
  2. B.₦3,750.00
  3. C.₦3,600.00
  4. D.₦3,300.00
Show the answer and explanation

Answer: A (₦3,900.00)

Explanation

Interest = 3000 × 6 × 5/100 = ₦900, so the amount is ₦3,900.00.

Open this question

Question 6

Fractions, Decimals and Approximation

Express the square root of 0.000144 in the standard form.

  1. A.1.2 × 10−4
  2. B.1.2 × 10−3
  3. C.1.2 × 10−2
  4. D.1.2 × 10−1
Show the answer and explanation

Answer: C (1.2 × 10−2)

Explanation

√0.000144 = 0.012 = 1.2 × 10−2.

Open this question

Question 7

Sets

Two sets are disjoint if

  1. A.they are both empty
  2. B.their union is an empty set
  3. C.their intersection is an empty set
  4. D.one of them is a subset of the other.
Show the answer and explanation

Answer: C (their intersection is an empty set)

Explanation

Disjoint sets have no element in common, so their intersection is empty.

Open this question

Question 8

Linear and Simultaneous Equations

Solve the following simultaneous equations: 2x + 3y = 7, x + 5y = 0.

  1. A.x = 5, y = −1
  2. B.x = 1/5, y = −1
  3. C.x = −1/5, y = 1
  4. D.x = −5, y = 1
Show the answer and explanation

Answer: A (x = 5, y = −1)

Explanation

From the second equation x = −5y. Then −10y + 3y = 7, so y = −1 and x = 5.

Open this question

Question 9

Linear and Simultaneous Equations

If 3/2x − 2/3x = 4, solve for x.

  1. A.4/5
  2. B.4/13
  3. C.5/24
  4. D.13/24
Show the answer and explanation

Answer: C (5/24)

Explanation

Over 6x: (9 − 4)/6x = 4, so 5 = 24x and x = 5/24.

Open this question

Question 10

Graphs of Functions

The following is the graph of a quadratic function. Find the co-ordinates of point P.

Diagram for this question
  1. A.(0, 4)
  2. B.(4, 0)
  3. C.(0, −4)
  4. D.(−4, 0)
Show the answer and explanation

Answer: A ((0, 4))

Explanation

P is where the curve y = x2 − 5x + 4 crosses the y-axis: x = 0 gives y = 4, so P is (0, 4).

Open this question

Question 11

Graphs of Functions

The following is the graph of a quadratic function. Find the values of x when y = 0.

Diagram for this question
  1. A.1, 3
  2. B.1, 4
  3. C.2, 3
  4. D.1, 6
Show the answer and explanation

Answer: B (1, 4)

Explanation

The curve cuts the x-axis at x = 1 and x = 4 (x2 − 5x + 4 = (x − 1)(x − 4)).

Open this question

Question 12

Linear and Simultaneous Equations

Five bottles of Fanta and two packets of biscuits cost Gh¢6.00. Three bottles of Fanta and four packets of biscuits cost Gh¢5.00. Find the cost of a bottle of Fanta.

  1. A.Gh¢0.50
  2. B.Gh¢1.00
  3. C.Gh¢1.50
  4. D.Gh¢5.00
Show the answer and explanation

Answer: B (Gh¢1.00)

Explanation

5f + 2b = 6 and 3f + 4b = 5. Doubling the first: 10f + 4b = 12; subtracting the second: 7f = 7, so f = Gh¢1.00.

Open this question

Question 14

Algebraic Expressions

Factorize x2 − 2x − 3xy + 6y completely.

  1. A.(x − 2)(3x − y)
  2. B.(x − 3y)(x − 2)
  3. C.(x − 2)(x + 3y)
  4. D.(3x + y)(x − 2)
Show the answer and explanation

Answer: B ((x − 3y)(x − 2))

Explanation

Group: x(x − 2) − 3y(x − 2) = (x − 2)(x − 3y).

Open this question

Question 15

Inequalities

Which of the following illustrates the solution of (3x + 4)/2 < x + 3?

Diagram for this question
  1. A.Diagram A
  2. B.Diagram B
  3. C.Diagram C
  4. D.Diagram D
Show the answer and explanation

Answer: D (Diagram D)

Explanation

Multiply by 2: 3x + 4 < 2x + 6, so x < 2. Use an open circle at 2 (2 is not included) and shade to the left.

Open this question

Question 16

Mensuration of Plane Shapes

The diameter of a bicycle wheel is 42 cm. If the wheel makes 16 complete revolutions, what will be the total distance covered by the wheel? [Take π = 22/7]

  1. A.672 cm
  2. B.1056 cm
  3. C.2112 cm
  4. D.4224 cm
Show the answer and explanation

Answer: C (2112 cm)

Explanation

One revolution = πd = 22/7 × 42 = 132 cm. 16 revolutions = 2112 cm.

Open this question

Question 17

Mensuration of Plane Shapes

PQRS is a trapezium. QR//PS, |PQ| = 5 cm, |QR| = 6 cm, |PS| = 10 cm and angle QPS = 42°. Calculate the perpendicular distance between the parallel sides.

Diagram for this question
  1. A.3.35 cm
  2. B.3.72 cm
  3. C.4.50 cm
  4. D.4.62 cm
Show the answer and explanation

Answer: A (3.35 cm)

Explanation

Height = 5 sin 42° = 5 × 0.6691 ≈ 3.35 cm.

Open this question

Question 18

Mensuration of Plane Shapes

PQRS is a trapezium. QR//PS, |PQ| = 5 cm, |QR| = 6 cm, |PS| = 10 cm and angle QPS = 42°. Calculate, correct to the nearest cm2, the area of the trapezium.

Diagram for this question
  1. A.27 cm2
  2. B.30 cm2
  3. C.36 cm2
  4. D.37 cm2
Show the answer and explanation

Answer: A (27 cm2)

Explanation

Area = ½(6 + 10) × 3.346 ≈ 26.8 ≈ 27 cm2.

Open this question

Question 19

Circle Theorems

In the diagram, |TP| = 12 cm and it is 6 cm from O, the centre of the circle. Calculate ∠TOP.

Diagram for this question
  1. A.120°
  2. B.90°
  3. C.60°
  4. D.45°
Show the answer and explanation

Answer: B (90°)

Explanation

The perpendicular from O bisects TP into 6 cm halves. Each half-angle has tan = 6/6 = 1, so it is 45°, and ∠TOP = 90°.

Open this question

Question 20

Angles and Polygons

The interior angles of a pentagon are (2x + 5)°, (x + 20)°, x°, (3x − 20)° and (x + 15)°. Find the value of x.

  1. A.80°
  2. B.70°
  3. C.65°
  4. D.40°
Show the answer and explanation

Answer: C (65°)

Explanation

A pentagon's angles add to 540°: 8x + 20 = 540, so x = 65.

Open this question

Question 21

Angles and Polygons

In the diagram, IG is parallel to JE, JÊF = 120° and FĤG = 130°. Find the angle marked t.

Diagram for this question
  1. A.40°
  2. B.70°
  3. C.80°
  4. D.100°
Show the answer and explanation

Answer: B (70°)

Explanation

Draw a line through F parallel to JE and IG. FE makes 180° − 120° = 60° with it and FH makes 180° − 130° = 50° with it (co-interior angles). The angles at F on that straight line add to 180°, so t = 180° − 60° − 50° = 70°.

Open this question

Question 22

Loci

If M and N are two fixed points in a plane, find the locus L = {P : PM = PN}.

  1. A.A line equal to MN
  2. B.A line parallel to MN
  3. C.Perpendicular bisector of MN
  4. D.A circle centre P, radius MN.
Show the answer and explanation

Answer: C (Perpendicular bisector of MN)

Explanation

Points equidistant from two fixed points lie on the perpendicular bisector of the line joining them.

Open this question

Question 23

Triangles and Quadrilaterals

Find the value of x in the diagram.

Diagram for this question
  1. A.50°
  2. B.30°
  3. C.22°
  4. D.17°
Show the answer and explanation

Answer: D (17°)

Explanation

The marked angles are the exterior angles of the polygon, which add to 360°: (x + 64) + 2x + (3x − 54) + 5x + 4x + 3x + (2x + 10) = 20x + 20 = 360, so x = 17.

Open this question

Question 24

Triangles and Quadrilaterals

In the diagram, |SQ| = 4 cm, |PT| = 7 cm, |TR| = 5 cm and ST//QR. If |SP| = x cm, find the value of x.

Diagram for this question
  1. A.5.6
  2. B.6.5
  3. C.6.6
  4. D.6.8
Show the answer and explanation

Answer: A (5.6)

Explanation

ST ∥ QR divides the sides in the same ratio: PS/SQ = PT/TR, so x/4 = 7/5 and x = 5.6.

Open this question

Question 25

Trigonometry

Given that sin 60° = √3/2 and cos 60° = 1/2, evaluate: (1 − sin 60°)/(1 + cos 60°)

  1. A.(2 + √3)/3
  2. B.(1 − √3)/3
  3. C.(1 + √3)/3
  4. D.(2 − √3)/3
Show the answer and explanation

Answer: D ((2 − √3)/3)

Explanation

(1 − √3/2)/(3/2) = ((2 − √3)/2) × (2/3) = (2 − √3)/3.

Open this question

Question 26

Bearings

Use the diagram to answer this question. Find the bearing of X from Y.

Diagram for this question
  1. A.300°
  2. B.240°
  3. C.120°
  4. D.60°
Show the answer and explanation

Answer: B (240°)

Explanation

The bearing of Y from X is 060°. The back bearing is 060° + 180° = 240°.

Open this question

Question 27

Bearings

Use the diagram to answer this question. If |XY| = 50 m, how far east of X is Y?

Diagram for this question
  1. A.25.5 m
  2. B.40.6 m
  3. C.40.8 m
  4. D.43.3 m
Show the answer and explanation

Answer: D (43.3 m)

Explanation

Y is on a bearing of 060° from X, so the distance east = 50 sin 60° ≈ 43.3 m.

Open this question

Question 28

Measures of Central Tendency

In an examination, Kofi scored x % in Physics, 50% in Chemistry and 70 % in Biology. If his mean score for the three subjects was 55 %, find x.

  1. A.40
  2. B.45
  3. C.55
  4. D.60
Show the answer and explanation

Answer: B (45)

Explanation

(x + 50 + 70)/3 = 55, so x + 120 = 165 and x = 45.

Open this question

Question 29

Measures of Central Tendency

What is the median of the following scores: 22, 41, 35, 63, 82, 74?

  1. A.82
  2. B.52
  3. C.49
  4. D.22
Show the answer and explanation

Answer: B (52)

Explanation

In order: 22, 35, 41, 63, 74, 82. The median is the mean of the middle two: (41 + 63)/2 = 52.

Open this question

Question 30

Fractions, Decimals and Approximation

Express 2.7864 × 10−3 to two significant figures.

  1. A.0.28
  2. B.0.27
  3. C.0.0028
  4. D.0.0027
Show the answer and explanation

Answer: C (0.0028)

Explanation

2.7864 × 10−3 = 0.0027864, which is 0.0028 to 2 significant figures.

Open this question

Question 31

Indices

If 92x = (1/3)(27x), find x.

  1. A.2
  2. B.1
  3. C.−1
  4. D.−2
Show the answer and explanation

Answer: C (−1)

Explanation

Powers of 3: 34x = 3−1 × 33x = 33x − 1, so 4x = 3x − 1 and x = −1.

Open this question

Question 32

Commercial Arithmetic

If 85% of x is ₦3230, what is the value of x?

  1. A.₦2745.50
  2. B.₦3714.50
  3. C.₦3800.00
  4. D.₦4845.00
Show the answer and explanation

Answer: C (₦3800.00)

Explanation

x = 3230 × 100/85 = ₦3800.00.

Open this question

Question 33

Mensuration of Solids

The capacity of a water tank is 1,800 litres. If the tank is in the form of a cuboid with base 600 cm by 150 cm, find the height of the tank.

  1. A.2 cm
  2. B.20 cm
  3. C.200 cm
  4. D.2000 cm
Show the answer and explanation

Answer: B (20 cm)

Explanation

1,800 litres = 1,800,000 cm3. Height = 1,800,000 ÷ (600 × 150) = 20 cm.

Open this question

Question 34

Mensuration of Plane Shapes

An arc of a circle subtends an angle of 60° at the centre. If the radius of the circle is 3 cm, find, in terms of π, the length of the arc.

  1. A.π cm
  2. B.2π cm
  3. C.3π cm
  4. D.6π cm
Show the answer and explanation

Answer: A (π cm)

Explanation

Arc = 60/360 × 2π × 3 = π cm.

Open this question

Question 35

Linear and Simultaneous Equations

Solve: (2x + 1)/6 − (3x − 1)/4 = 0.

  1. A.1
  2. B.1/5
  3. C.−1/5
  4. D.−1
Show the answer and explanation

Answer: A (1)

Explanation

Multiply by 12: 2(2x + 1) − 3(3x − 1) = 0, so 4x + 2 − 9x + 3 = 0, −5x = −5 and x = 1.

Open this question

Question 36

Inequalities

If x is a positive integer, list the values of x which satisfy the equations 3x − 4 < 6 and x − 1 > 0.

  1. A.{1, 2, 3}
  2. B.{2, 3}
  3. C.{2, 3, 4}
  4. D.{2, 3, 4, 5}
Show the answer and explanation

Answer: B ({2, 3})

Explanation

3x < 10 gives x < 3⅓ and x − 1 > 0 gives x > 1. The integers between are 2 and 3.

Open this question

Question 37

Quadratic Equations

If c and k are the roots of 6 − x − x2 = 0, find c + k.

  1. A.2
  2. B.1
  3. C.−1
  4. D.−3
Show the answer and explanation

Answer: C (−1)

Explanation

6 − x − x2 = (2 − x)(3 + x), so the roots are 2 and −3, and c + k = −1.

Open this question

Question 38

Circle Theorems

In the diagram, angle 200° is subtended at the centre of the circle. Find the value of x.

Diagram for this question
  1. A.30°
  2. B.50°
  3. C.80°
  4. D.100°
Show the answer and explanation

Answer: B (50°)

Explanation

The angle at the top of the circle is half the non-reflex angle at the centre: ½(360° − 200°) = 80°. The radii make isosceles triangles, so this top angle equals 30° + x. Hence x = 50°.

Open this question

Question 39

Angles and Polygons

Each of the interior angles of a regular polygon is 140°. Calculate the sum of all the interior angles of the polygon.

  1. A.1080°
  2. B.1260°
  3. C.1800°
  4. D.2160°
Show the answer and explanation

Answer: B (1260°)

Explanation

Each exterior angle is 40°, so n = 360/40 = 9 sides. Sum = 9 × 140° = 1260°.

Open this question

Question 40

Mensuration of Solids

A bucket holds 10 litres of water. How many buckets of water will fill a reservoir of size 8 m × 7 m × 5 m. (1 litre = 1000 cm3).

  1. A.28
  2. B.280
  3. C.2800
  4. D.28000
Show the answer and explanation

Answer: D (28000)

Explanation

Volume = 280 m3 = 280,000 litres (1 m3 = 1000 litres). 280,000 ÷ 10 = 28,000 buckets.

Open this question

Question 41

Probability

A box contains black, white and red identical balls. The probability of picking a black ball at random from the box is 3/10 and the probability of picking a white ball at random is 2/5. If there are 30 balls in the box, how many of them are red?

  1. A.3
  2. B.7
  3. C.9
  4. D.12
Show the answer and explanation

Answer: C (9)

Explanation

P(red) = 1 − 3/10 − 4/10 = 3/10, so there are 3/10 × 30 = 9 red balls.

Open this question

Question 42

Data Presentation

The pie chart shows the distribution of 4320 students who graduated from four Departments in a University. How many students graduated from the Science Department?

Diagram for this question
  1. A.840
  2. B.864
  3. C.920
  4. D.960
Show the answer and explanation

Answer: B (864)

Explanation

Science angle = 360° − (100° + 80° + 108°) = 72°. 72/360 × 4320 = 864.

Open this question

Question 43

Probability

The pie chart shows the distribution of 4320 students who graduated from four Departments in a University. If a student is picked at random from the four departments, what is the probability that he is not from the Education Department?

Diagram for this question
  1. A.3/10
  2. B.2/9
  3. C.5/18
  4. D.7/10
Show the answer and explanation

Answer: D (7/10)

Explanation

Education has 108° of 360°, i.e. 3/10. So P(not Education) = 1 − 3/10 = 7/10.

Open this question

Question 44

Surds

Simplify: ½√32 − √18 + √2.

  1. A.0
  2. B.√2
  3. C.2√2
  4. D.4√2
Show the answer and explanation

Answer: A (0)

Explanation

½√32 = 2√2 and √18 = 3√2, so 2√2 − 3√2 + √2 = 0.

Open this question

Question 45

Circle Theorems

From the diagram, which of the following statements is/are correct?
I. XQ is a radius of a circle centre Q.
II. |XQ| = |QY|
III. |QX| = |XY|

Diagram for this question
  1. A.I only
  2. B.I and II only
  3. C.II and III only
  4. D.I, II and III.
Show the answer and explanation

Answer: D (I, II and III.)

Explanation

The large arc is drawn with centre Q and radius QX, so I is true and QY = QX (II). The small arc cutting it at Y is drawn from X with the same radius, so XY = QX (III).

Open this question

Question 46

Triangles and Quadrilaterals

Find the value of X in the diagram.

Diagram for this question
  1. A.50°
  2. B.60°
  3. C.70°
  4. D.80°
Show the answer and explanation

Answer: D (80°)

Explanation

At the middle vertex the angle between the two arms (on the right) is 360° − 250° = 110°. Split it with the parallel line through the vertex: the lower part is 30° (alternate to the 30°), so the upper part is 80°, and x equals it (alternate angles).

Open this question

Question 47

Triangles and Quadrilaterals

The angles of a triangle are (x + 10)°, (2x − 40)° and (3x − 90)°. Which of the following accurately describes the triangle?

  1. A.It is a scalene triangle
  2. B.It is a right angled isosceles triangle
  3. C.It is an equilateral triangle
  4. D.It is an isosceles triangle but not right angled.
Show the answer and explanation

Answer: C (It is an equilateral triangle)

Explanation

6x − 120 = 180 gives x = 50, so the angles are 60°, 60° and 60°: equilateral.

Open this question

Question 48

Sets

Which shaded region in the following diagrams represents (P ∪ Q) ∩ R?

Diagram for this question
  1. A.Diagram A
  2. B.Diagram B
  3. C.Diagram C
  4. D.Diagram D
Show the answer and explanation

Answer: C (Diagram C)

Explanation

First take P ∪ Q (everything in P or Q), then keep only the part that is also inside R. That is the top part of circle R overlapping P and Q, as in C.

Open this question

Question 49

Algebraic Expressions

Simplify: (x − 3y)2 − (x + 3y)2.

  1. A.2(x + 3y)
  2. B.2(x − 3y)
  3. C.−12xy
  4. D.6xy
Show the answer and explanation

Answer: C (−12xy)

Explanation

(x2 − 6xy + 9y2) − (x2 + 6xy + 9y2) = −12xy.

Open this question

Question 50

Quadratic Equations

Find the quadratic equation whose roots are −1/2 and 3.

  1. A.2x2 − 2x + 3 = 0
  2. B.2x2 − 2x − 3 = 0
  3. C.2x2 − 5x + 3 = 0
  4. D.2x2 − 5x − 3 = 0
Show the answer and explanation

Answer: D (2x2 − 5x − 3 = 0)

Explanation

(2x + 1)(x − 3) = 0 gives 2x2 − 5x − 3 = 0.

Open this question

Theory question 101

Surds

(a) Given that (√3 − 5√2)(√3 + √2) = a + b√6, find a and b.
(b) If (21−y × 2y−1)/2y+2 = 82−3y, find y.

Show the model answer
Model answer

(a) Expand: 3 + √6 − 5√6 − 5 × 2 = −7 − 4√6, so a = −7 and b = −4.
(b) Left side = 2(1 − y) + (y − 1) − (y + 2) = 2−y − 2; right side = 23(2 − 3y) = 26 − 9y.
−y − 2 = 6 − 9y → 8y = 8 → y = 1.

Explanation

Write everything as a power of 2 and equate the indices.

Open this question

Theory question 102

Trigonometry

(a) If 9 cos x° − 7 = 1 and 0° ≤ x ≤ 90°, find x.
(b) Given that x is an integer, find the three greatest values of x which satisfy the inequality 7x < 2x − 13.

Show the model answer
Model answer

(a) 9 cos x = 8 → cos x = 0.8889 → x ≈ 27.3°.
(b) 5x < −13 → x < −2.6. The three greatest integers are −3, −4 and −5.

Explanation

Be careful: the greatest integers less than −2.6 are −3, −4, −5.

Open this question

Theory question 103

Measures of Central Tendency

The table shows the number of children per family in a community.
No. of children: 0, 1, 2, 3, 4, 5
No. of families: 3, 5, 7, 4, 3, 2
(a) Find the: (i) mode; (ii) third quartile; (iii) probability that a family has at least 2 children.
(b) If a pie chart were to be drawn for the data, what would be the sectorial angle representing families with one child?

Show the model answer
Model answer

Total families = 24.
(a)(i) Mode = 2 children (highest frequency, 7).
(ii) Third quartile = ¾ × 24 = 18th family. Cumulative frequencies 3, 8, 15, 19, …, so the 18th family has 3 children: Q3 = 3.
(iii) At least 2 children: 7 + 4 + 3 + 2 = 16. P = 16/24 = 2/3.
(b) 5/24 × 360° = 75°.

Explanation

Use cumulative frequency to locate the quartile.

Open this question

Theory question 104

Sets

(a) Out of 30 candidates applying for a post, 17 have degrees, 15 diplomas and 4 neither degree nor diploma. How many of them have both?
(b) In triangle PQR, M and N are points on the sides PQ and PR respectively such that MN is parallel to QR. If ∠PRQ = 75°, PN = QN and ∠PNQ = 125°, determine (i) ∠NQR; (ii) ∠NPM.

Show the model answer
Model answer

(a) 30 − 4 = 26 have at least one. Both = 17 + 15 − 26 = 6.
(b)(i) PNR is a straight line, so ∠QNR = 180° − 125° = 55°. In ΔNQR: ∠NQR = 180° − 55° − 75° = 50°.
(ii) ΔPNQ is isosceles (PN = QN), so ∠NPQ = ∠NQP = (180° − 125°)/2 = 27.5°. M is on PQ, so ∠NPM = 27.5°.

Explanation

Use n(D ∪ Dip) = n(D) + n(Dip) − n(both).

Open this question

Theory question 105

Mensuration of Solids

In the diagram, ABCDEF is a triangular prism. ∠ABC = ∠DEF = 90°, |AB| = 24 cm, |BC| = 7 cm and |CD| = 40 cm. Calculate: (a) |AC|; (b) the total surface area of the prism.

Diagram for this question
Show the model answer
Model answer

(a) |AC| = √(242 + 72) = √625 = 25 cm.
(b) Two triangular ends: 2 × ½ × 24 × 7 = 168 cm2.
Three rectangles: 40 × (24 + 7 + 25) = 40 × 56 = 2240 cm2.
Total surface area = 2408 cm2.

Explanation

The rectangular faces together equal the perimeter of the triangle times the length.

Open this question

Theory question 106

Logarithms

(a) If log 5 = 0.6990, log 7 = 0.8451 and log 8 = 0.9031, calculate: log ((35 × 49)/(40 ÷ 56))
(b) For a musical show, x children were present. There were 60 more adults than children. An adult paid D5 and a child D2. If a total of D1280 was collected, calculate the (i) value of x; (ii) ratio of the number of children to the number of adults; (iii) average amount paid per person; (iv) percentage profit if the organisers spent D720 on the show.

Show the model answer
Model answer

(a) (35 × 49)/(40 ÷ 56) = (5 × 7)(72)(8 × 7)/(8 × 5) = 74.
log 74 = 4 × 0.8451 = 3.3804.
(b)(i) 2x + 5(x + 60) = 1280 → 7x = 980 → x = 140.
(ii) Children : adults = 140 : 200 = 7 : 10.
(iii) 1280 ÷ 340 ≈ D3.76 per person.
(iv) Profit = 1280 − 720 = D560; percentage = 560/720 × 100% ≈ 77.8%.

Explanation

Break each number into prime factors before using the logs.

Open this question

Theory question 107

Trigonometry

(a) A woman looking out from the window of a building at a height of 30 m, observed that the angle of depression of the top of a flag pole was 44°. If the foot of the pole is 25 m from the foot of the building and on the same horizontal ground, find, correct to the nearest whole number, the (i) angle of depression of the foot of the pole from the woman; (ii) height of the flag pole.
(b) In the diagram, O is the centre of the circle, ∠OQR = 32° and ∠TPQ = 15°. Calculate: (i) ∠QPR; (ii) ∠TQO.

Diagram for this question
Show the model answer
Model answer

(a)(i) tan θ = 30/25 = 1.2 → θ ≈ 50°.
(ii) Drop from the window to the level of the pole's top: 30 − h = 25 tan 44° ≈ 24.14, so h ≈ 5.86 ≈ 6 m.
(b)(i) OQ = OR, so ∠ORQ = 32° and ∠QOR = 180° − 64° = 116°. ∠QPR = ½ × 116° = 58°.
(ii) ∠TOQ = 2 × ∠TPQ = 30°. OT = OQ, so ∠TQO = (180° − 30°)/2 = 75°.

Explanation

Radii make isosceles triangles; the angle at the centre is twice the angle at the circumference.

Open this question

Theory question 108

Data Presentation

The marks scored by 50 students in a Geography examination are as follows:
60 54 40 67 53 73 37 55 62 43
44 69 39 32 45 58 48 67 39 51
46 59 40 52 61 48 23 60 59 47
65 58 74 47 40 59 68 51 50 50
71 51 26 36 38 70 46 40 51 42
(a) Using class intervals 21 − 30, 31 − 40, …, prepare a frequency distribution table.
(b) Calculate the mean mark of the distribution.
(c) What percentage of the students scored more than 60%?

Show the model answer
Model answer

(a) 21–30: 2; 31–40: 10; 41–50: 12; 51–60: 15; 61–70: 8; 71–80: 3 (total 50).
(b) Class marks 25.5, 35.5, 45.5, 55.5, 65.5, 75.5: Σfx = 51 + 355 + 546 + 832.5 + 524 + 226.5 = 2535. Mean = 2535/50 = 50.7.
(c) Marks above 60: 11 students (from the list). 11/50 × 100% = 22%.

Explanation

Check the frequencies add up to 50 before working out the mean.

Open this question

Theory question 109

Algebraic Expressions

(a) Simplify (x + 2)/(x − 2) − (x + 3)/(x − 1)
(b) The graph of the equation y = Ax2 + Bx + C passes through the points (0, 0), (1, 4) and (2, 10). Find the: (i) value of C; (ii) values of A and B; (iii) co-ordinates of the other point where the graph cuts the x-axis.

Show the model answer
Model answer

(a) [(x + 2)(x − 1) − (x + 3)(x − 2)]/[(x − 2)(x − 1)] = [(x2 + x − 2) − (x2 + x − 6)]/[(x − 2)(x − 1)] = 4/[(x − 2)(x − 1)].
(b)(i) (0, 0): C = 0.
(ii) A + B = 4 and 4A + 2B = 10 → 2A = 2 → A = 1, B = 3.
(iii) y = x2 + 3x = x(x + 3) = 0 → the other point is (−3, 0).

Explanation

Substitute each point into the equation to get simultaneous equations.

Open this question

Theory question 110

Constructions

(a) Using ruler and a pair of compasses only, construct: (i) quadrilateral PQRS such that |PQ| = 10 cm, |QR| = 8 cm, |PS| = 6 cm, ∠PQR = 60° and ∠QPS = 75°; (ii) the locus l1 of points equidistant from QR and RS; (iii) locus l2 of points equidistant from R and S.
(b) Measure |RS|.

Show the model answer
Model answer

(a)(i) Draw PQ = 10 cm. Construct 60° at Q and mark QR = 8 cm; construct 75° at P (60° + half of 30°) and mark PS = 6 cm. Join RS.
(ii) l1 is the bisector of ∠QRS.
(iii) l2 is the perpendicular bisector of RS.
(b) |RS| ≈ 4.6 cm.

Explanation

Points equidistant from two lines lie on the bisector of the angle between them.

Open this question

Theory question 111

Mensuration of Plane Shapes

(a) A circle is inscribed in a square. If the sum of the perimeter of the square and the circumference of the circle is 100 cm, calculate the radius of the circle. [Take π = 22/7]
(b) A rope 60 cm long is made to form a rectangle. If the length is 4 times its breadth, calculate, correct to one decimal place, the (i) length; (ii) diagonal of the rectangle.

Show the model answer
Model answer

(a) The square's side is 2r. 8r + 2 × 22/7 × r = 100 → r(56 + 44)/7 = 100 → r = 7 cm.
(b) 2(l + b) = 60 and l = 4b → 10b = 60 → b = 6 cm.
(i) l = 24.0 cm.
(ii) Diagonal = √(242 + 62) = √612 ≈ 24.7 cm.

Explanation

A circle inscribed in a square has diameter equal to the side of the square.

Open this question

Theory question 112

Trigonometry

(a) Copy and complete the table of values for y = sin x + 2 cos x, correct to one decimal place.
x: 0°, 30°, 60°, 90°, 120°, 150°, 180°, 210°, 240°
y: __, 2.2, __, __, __, −1.2, −2.0, __, −1.9
(b) Using a scale of 2 cm to 30° on the x-axis and 2 cm to 0.5 units on the y-axis, draw the graph of y = sin x + 2 cos x for 0° ≤ x ≤ 240°.
(c) Use your graph to solve the equation: (i) sin x + 2 cos x = 0; (ii) sin x = 2.1 − 2 cos x.
(d) From the graph, find y when x = 171°.

Show the model answer
Model answer

(a) 0°: 2.0; 60°: 1.9; 90°: 1.0; 120°: −0.1; 210°: −2.2 (given: 30°: 2.2, 150°: −1.2, 180°: −2.0, 240°: −1.9).
(b) Plot and join with a smooth curve.
(c)(i) Where the curve crosses the x-axis: x ≈ 117°.
(ii) Rewrite as sin x + 2 cos x = 2.1; draw y = 2.1: x ≈ 7° and x ≈ 47°.
(d) At x = 171°, y ≈ −1.8.
(Accept graph readings close to these.)

Explanation

For (c)(ii), move 2 cos x to the left so the equation matches the graph.

Open this question

Theory question 113

Progressions

(a) How many numbers between 75 and 500 are divisible by 7?
(b) The 8th term of an Arithmetic Progression (A.P) is 5 times the third term while the 7th term is 9 greater than the 4th term. Write the first five terms of the A.P.

Show the model answer
Model answer

(a) The multiples of 7 run from 77 (7 × 11) to 497 (7 × 71): 71 − 11 + 1 = 61 numbers.
(b) a + 7d = 5(a + 2d) → 4a = −3d. (a + 6d) − (a + 3d) = 9 → d = 3, so a = −9/4.
First five terms: −2¼, ¾, 3¾, 6¾, 9¾.

Explanation

Count multiples of 7 as an AP from 77 to 497 with difference 7.

Open this question

Theory question 114

Modular Arithmetic

(Questions 14 and 15 are for candidates in Ghana, Sierra Leone and The Gambia only.)
(a) Copy and complete the multiplication table modulo 5 on the set {1, 2, 3, 4}.
(b) From your table; (i) solve the expression 2n * 4 ≡ 3; (ii) find the value of n for which 2 * (3 * n) ≡ 2.
(c) The functions f and g are defined as f : x → x − 2 and g : x → 2x2 − 1. Solve: (i) f(x) = g(−1/2); (ii) f(x) + g(x) = 0.

Show the model answer
Model answer

(a) Rows (× 1, 2, 3, 4): 1: 1, 2, 3, 4; 2: 2, 4, 1, 3; 3: 3, 1, 4, 2; 4: 4, 3, 2, 1.
(b)(i) 2n * 4 = 8n ≡ 3n ≡ 3 (mod 5), so n = 1.
(ii) 2 * (3 * n) = 6n ≡ n ≡ 2, so n = 2.
(c)(i) g(−½) = 2(¼) − 1 = −½. x − 2 = −½ → x = 3/2.
(ii) x − 2 + 2x2 − 1 = 0 → 2x2 + x − 3 = 0 → (2x + 3)(x − 1) = 0 → x = 1 or x = −3/2.

Explanation

In modulo 5, replace each product by its remainder on division by 5.

Open this question

Theory question 115

Vectors and Transformations

(a) P(7, 4) is a vertex of triangle PQR. If QP = (3, 5) and PR = (−3, 4), find: (i) the co-ordinates of Q; (ii) PN where N is the midpoint of QR.
(b) A straight line passes through the points (1, 4) and (3, 0). Find the (i) gradient; (ii) equation of the line.

Show the model answer
Model answer

(a)(i) Q = P − QP = (7 − 3, 4 − 5) = (4, −1).
(ii) R = P + PR = (4, 8). N = midpoint of QR = (4, 3.5). PN = (4 − 7, 3.5 − 4) = (−3, −0.5).
(b)(i) Gradient = (0 − 4)/(3 − 1) = −2.
(ii) y − 4 = −2(x − 1) → y = −2x + 6.

Explanation

A vector QP = (position of P) − (position of Q).

Open this question