JAMB Mathematics 1998 past questions and answers

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

Question 1

Number Bases

If 10112 + X7 = 2510, solve for X

  1. A.14
  2. B.20
  3. C.24
  4. D.25
Show the answer and explanation

Answer: B (20)

Explanation

1011₂ = 8 + 2 + 1 = 11, so X₇ must equal 25 − 11 = 14 in base ten. 14 = 2 × 7 + 0, which is 20 in base 7.

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Question 2

Fractions, Decimals and Approximation

Evaluate (1/0.03 ÷ 1/0.024)−1 correct to 2 decimal places.

  1. A.3.76
  2. B.1.25
  3. C.0.94
  4. D.0.75
Show the answer and explanation

Answer: B (1.25)

Explanation

1/0.03 ÷ 1/0.024 = 0.024/0.03 = 0.8. Its reciprocal is 1/0.8 = 1.25.

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Question 3

Indices

If b3 = a−2 and c1/3 = a1/2b, express c in terms of a.

  1. A.a−1/2
  2. B.a1/2
  3. C.a3/2
  4. D.a−2/3
Show the answer and explanation

Answer: A (a−1/2)

Explanation

b = a^(−2/3), so c^(1/3) = a^(1/2) × a^(−2/3) = a^(−1/6). Cubing gives c = a^(−1/2).

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Question 4

Logarithms

Given that log4(y − 1) + log4(½x) = 1 and log2(y + 1) + log2x = 2, solve for x and y respectively.

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

Answer: C (−2, −3)

Explanation

The first equation gives (y − 1)(x/2) = 4, so xy − x = 8. The second gives x(y + 1) = 4, so xy + x = 4. Subtracting gives 2x = −4, so x = −2 and then y = −3.

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Question 5

Surds

Find the value of K if K/(√3 + √2) = K√3 − 2

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

Answer: D (√2)

Explanation

K = (K√3 − 2)(√3 + √2) = 3K + K√6 − 2√3 − 2√2, so K(2 + √6) = 2(√3 + √2). Since 2 + √6 = √2(√2 + √3), K = 2/√2 = √2.

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Question 6

Mensuration of Solids

A market woman sells oil in cylindrical tins 10cm deep and 6cm in diameter at N15.00 each. If she bought a full cylindrical jug 18cm deep and 10cm in diameter for N50.00, how much did she make by selling all the oil?

  1. A.N62.50
  2. B.N35.00
  3. C.N31.00
  4. D.N25.00
Show the answer and explanation

Answer: D (N25.00)

Explanation

Tin volume = π × 3² × 10 = 90π; jug volume = π × 5² × 18 = 450π. The jug fills 5 tins, which sell for 5 × N15 = N75, so she makes N75 − N50 = N25.

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Question 7

Algebraic Expressions

A man is paid r naira per hour for normal work and double rate for overtime. If he does a 35-hour week which includes q hours of overtime, what is the weekly earning in naira.

  1. A.r(35 + q)
  2. B.q(35r − q)
  3. C.q(35 + r)
  4. D.r(35r − q)
Show the answer and explanation

Answer: A (r(35 + q))

Explanation

He works 35 − q normal hours at r and q overtime hours at 2r: (35 − q)r + 2qr = 35r + qr = r(35 + q).

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Question 8

Sets

Given the universal set U = {1, 2, 3, 4, 5, 6} and the sets P = {1, 2, 3, 4}, Q = {3, 4, 5} and R = {2, 4, 6}. Find P ∪ (Q ∪ R)′.

  1. A.{4}
  2. B.{1, 2, 3, 4}
  3. C.{1, 2, 3, 5, 6}
  4. D.{1, 2, 3, 4, 5, 6}
Show the answer and explanation

Answer: B ({1, 2, 3, 4})

Explanation

Q ∪ R = {2, 3, 4, 5, 6}, so its complement is {1}. Then P ∪ {1} = {1, 2, 3, 4}.

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Question 9

Sets

In the diagram above, the shaded region is

Diagram for this question
  1. A.(P ∩ Q) ∪ R
  2. B.(P ∩ Q) ∩ R
  3. C.(P ∩ Q′) ∩ R
  4. D.(R ∩ Q′) ∪ R
Show the answer and explanation

Answer: C ((P ∩ Q′) ∩ R)

Explanation

The shaded part lies inside both P and R but outside Q, which is (P ∩ Q′) ∩ R.

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Question 10

Polynomials

When the expression pm2 + qm + 1 is divided by (m − 1), it has a remainder 2 and when divided by (m + 1) the remainder is 4. Find p and q respectively.

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

Answer: A (2, −1)

Explanation

By the remainder theorem, p + q + 1 = 2 and p − q + 1 = 4. So p + q = 1 and p − q = 3, giving p = 2 and q = −1.

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Question 11

Algebraic Expressions

Factorize r2 − r(2p + q) + 2pq.

  1. A.(r − 2q)(2r − p)
  2. B.(r − q)(r + p)
  3. C.(r − q)(r − 2p)
  4. D.(2r − q)(r + p)
Show the answer and explanation

Answer: C ((r − q)(r − 2p))

Explanation

r² − 2pr − qr + 2pq = r(r − 2p) − q(r − 2p) = (r − q)(r − 2p).

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Question 12

Surds

Solve the equation √x − √(x − 2) − 1 = 0

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

Answer: D (9/4)

Explanation

√x = 1 + √(x − 2). Squaring: x = 1 + 2√(x − 2) + x − 2, so √(x − 2) = 1/2, x − 2 = 1/4 and x = 9/4.

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Question 13

Inequalities

Find the range of values of m for which the roots of the equation 3x2 − 3mx + (m2 − m − 3) = 0 are real.

  1. A.−1 ≤ m ≤ 7
  2. B.−2 ≤ m ≤ 6
  3. C.−3 ≤ m ≤ 9
  4. D.−4 ≤ m ≤ 8
Show the answer and explanation

Answer: B (−2 ≤ m ≤ 6)

Explanation

Real roots need b² − 4ac ≥ 0: 9m² − 12(m² − m − 3) ≥ 0, i.e. m² − 4m − 12 ≤ 0, so (m − 6)(m + 2) ≤ 0 and −2 ≤ m ≤ 6.

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Question 14

Algebraic Expressions

make a/x the subject of formula (x + a)/(x − a) = m

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

Answer: A ((m − 1)/(m + 1))

Explanation

x + a = mx − ma, so a(1 + m) = x(m − 1) and a/x = (m − 1)/(m + 1).

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Question 15

Polynomials

Divide 2x3 + 11x2 + 17x + 6 by 2x + 1

  1. A.x2 + 5x + 6
  2. B.2x2 + 5x + 6
  3. C.2x2 − 5x + 6
  4. D.x2 − 5x + 6
Show the answer and explanation

Answer: A (x2 + 5x + 6)

Explanation

Long division gives x² + 5x + 6 with no remainder; check: (2x + 1)(x² + 5x + 6) = 2x³ + 11x² + 17x + 6.

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Question 16

Polynomials

Express in partial fractions (11x + 2)/(6x2 − x − 1)

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

Answer: D (1/(3x + 1) + 3/(2x − 1))

Explanation

6x² − x − 1 = (3x + 1)(2x − 1). Write 11x + 2 = A(2x − 1) + B(3x + 1); x = ½ gives B = 3 and x = −⅓ gives A = 1.

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Question 17

Inequalities

If x is a positive real number, find the range of values for which 1/3x + ½ > 1/4x

  1. A.x > −1/6
  2. B.x > 0
  3. C.0 < x < 4
  4. D.0 < x < 1/6
Show the answer and explanation

Answer: B (x > 0)

Explanation

Since x > 0, multiply through by 12x: 4 + 6x > 3, so x > −1/6. Every positive number satisfies this, so the solution is all x > 0.

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Question 18

Inequalities

The shaded area above represents

Diagram for this question
  1. A.x ≥ 0, 3y + 2x ≥ 6
  2. B.x ≥ 0, y ≥ 3, 3x + 2y ≥ 6
  3. C.x ≥ 2, y ≥ 0, 3x + 2y ≥ 6
  4. D.x ≥ 0, y ≥ 0, 3x + 2y ≥ 6
Show the answer and explanation

Answer: D (x ≥ 0, y ≥ 0, 3x + 2y ≥ 6)

Explanation

The line through (0, 3) and (2, 0) is 3x + 2y = 6. The shading is above this line and in the first quadrant, so x ≥ 0, y ≥ 0 and 3x + 2y ≥ 6.

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Question 19

Progressions

If p + 1, 2p − 10, 1 − 4p2 are three consecutive terms of an arithmetic progression, find the possible values of p.

  1. A.−4, 2
  2. B.−3, 4/11
  3. C.−11/4, 2
  4. D.5, −3
Show the answer and explanation

Answer: C (−11/4, 2)

Explanation

For an AP, 2(2p − 10) = (p + 1) + (1 − 4p²). This gives 4p² + 3p − 22 = 0, i.e. (4p + 11)(p − 2) = 0, so p = 2 or −11/4.

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Question 20

Progressions

The sum of the first three terms of a geometric progression is half its sum to infinity. Find the positive common ratio of the progression.

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

Answer: D (1/∛2)

Explanation

a(1 − r³)/(1 − r) = ½ × a/(1 − r), so 1 − r³ = ½, r³ = ½ and r = 1/∛2.

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Question 21

Binary Operations

The identity element with respect to the element shown in the table above is

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

Answer: B (q)

Explanation

The identity e satisfies e ⊗ x = x for every x. The row for q reads p, q, r, s, the same as the heading row, so q is the identity.

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Question 22

Binary Operations

The binary operation ∗ is defined by x∗y = xy − y − x for all real values x and y. If x∗3 = 2∗x, find x.

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

Answer: C (1)

Explanation

x∗3 = 3x − 3 − x = 2x − 3 and 2∗x = 2x − x − 2 = x − 2. So 2x − 3 = x − 2, giving x = 1.

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Question 23

Matrices and Determinants

The determinant of matrix
( x 1 0 )
( 1−x 2 3 )
( 1 1+x 4 )
in terms of x is.

  1. A.−3x2 − 17
  2. B.−3x2 + 9x − 1
  3. C.3x2 + 17
  4. D.3x2 − 9x + 5
Show the answer and explanation

Answer: B (−3x2 + 9x − 1)

Explanation

Expand along the first row: x[2(4) − 3(1 + x)] − 1[4(1 − x) − 3] = x(5 − 3x) − (1 − 4x) = −3x² + 9x − 1.

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Question 24

Matrices and Determinants

Let I = (1 0 / 0 1), P = (2 3 / 4 5), Q = (u 4+u / −2v v) be 2 × 2 matrices such that PQ = I. Find (u, v)
(Rows are separated by /.)

  1. A.(−5/2, −1)
  2. B.(−5/2, 3/2)
  3. C.(−5/6, 1)
  4. D.(5/2, 2/3)
Show the answer and explanation

Answer: A ((−5/2, −1))

Explanation

From PQ = I: 2u − 6v = 1 and 4u − 10v = 0. The second gives u = 5v/2; substituting, −v = 1, so v = −1 and u = −5/2.

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Question 25

Circle Theorems

In the diagram above, PR is a diameter of the circle PQRS. PST and QRT are straight lines. Find ∠QSR

Diagram for this question
  1. A.20°
  2. B.25°
  3. C.30°
  4. D.35°
Show the answer and explanation

Answer: B (25°)

Explanation

∠PSR = 90° (angle in a semicircle), so ∠RST = 90° and ∠SRT = 60°. Then ∠QRS = 120°, so ∠QPS = 60° (cyclic quadrilateral) and ∠QPR = 60° − 35° = 25°. ∠QSR = ∠QPR = 25° (same segment).

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Question 26

Triangles and Quadrilaterals

In the diagram above, PQ||ST and ∠PQR = 120°. ∠RST = 130°. Find the angle marked x

Diagram for this question
  1. A.50°
  2. B.65°
  3. C.70°
  4. D.80°
Show the answer and explanation

Answer: C (70°)

Explanation

Draw a line through R parallel to PQ. The angles it makes with RQ and RS are 180° − 120° = 60° and 180° − 130° = 50°. So x = 180° − 60° − 50° = 70°.

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Question 27

Mensuration of Plane Shapes

In the figure above, PQST is a parallelogram and TSR is a straight line. If the area of ΔQRS is 20cm2, find the area of the trapezium PQRT

Diagram for this question
  1. A.35cm2
  2. B.65cm2
  3. C.70cm2
  4. D.140cm2
Show the answer and explanation

Answer: C (70cm2)

Explanation

½ × 8 × h = 20 gives the height h = 5 cm. PQ = TS = 10 cm and TR = 18 cm, so the trapezium's area = ½(10 + 18) × 5 = 70 cm².

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Question 28

Circle Theorems

TQ is tangent to a circle XYTR, ∠YXT = 32°, ∠RTQ = 40°. Find ∠YTR

Diagram for this question
  1. A.108°
  2. B.121°
  3. C.140°
  4. D.148°
Show the answer and explanation

Answer: A (108°)

Explanation

By the alternate segment theorem ∠RXT = ∠RTQ = 40°, so ∠YXR = 32° + 40° = 72°. Opposite angles of cyclic quadrilateral XYTR add to 180°, so ∠YTR = 108°.

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Question 29

Mensuration of Plane Shapes

A chord of a circle radius √3cm subtends an angle of 60° on the circumference of the circle. Find the length of the chord.

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

Answer: D (3cm)

Explanation

The angle at the centre is 120°. Half the chord = √3 × sin 60° = 3/2, so the chord is 3 cm.

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Question 30

Mensuration of Solids

A cylindrical drum of diameter 56cm contains 123.2 litres of oil when full. Find the height of the drum in centimetres. (π = 22/7)

  1. A.12.5
  2. B.25.0
  3. C.45.0
  4. D.50.0
Show the answer and explanation

Answer: D (50.0)

Explanation

123.2 litres = 123 200 cm³. Base area = (22/7) × 28² = 2464 cm², so height = 123 200 ÷ 2464 = 50 cm.

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Question 31

Loci

The locus of all points at a distance 8cm from a point N passes through points T and S. If S equi-distant from T and N, find the area of triangle STN.

  1. A.4√3cm2
  2. B.16√3cm2
  3. C.32cm2
  4. D.64cm2
Show the answer and explanation

Answer: B (16√3cm2)

Explanation

NT = NS = 8 cm (radius) and ST = SN = 8 cm, so the triangle is equilateral with side 8 cm. Area = (√3/4) × 64 = 16√3 cm².

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Question 32

Coordinate Geometry

If the distance between the points (x, 3) and (−x, 2) is 5. Find x.

  1. A.6.0
  2. B.2.5
  3. C.√6
  4. D.3
Show the answer and explanation

Answer: C (√6)

Explanation

(2x)² + 1² = 25, so 4x² = 24, x² = 6 and x = √6.

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Question 33

Coordinate Geometry

The midpoint of the segment of the line y = 4x + 3 which lies between the x-axis and the y-axis is

  1. A.(−3/2, 3/2)
  2. B.(−2/3, 3/2)
  3. C.(3/8, 3/2)
  4. D.(−3/8, 3/2)
Show the answer and explanation

Answer: D ((−3/8, 3/2))

Explanation

The line meets the x-axis at (−3/4, 0) and the y-axis at (0, 3). The midpoint is (−3/8, 3/2).

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Question 35

Trigonometry

In the diagram above QTR is a straight line and ∠PQT = 30°. Find the sine of ∠PTR

Diagram for this question
  1. A.8/15
  2. B.2/3
  3. C.3/4
  4. D.15/16
Show the answer and explanation

Answer: D (15/16)

Explanation

In triangle PQT, sin∠PTQ/PQ = sin 30°/PT, so sin∠PTQ = (15 × ½)/8 = 15/16. ∠PTR = 180° − ∠PTQ has the same sine.

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Question 36

Trigonometry

For what value of x does 6 sin(2x − 25)° attain its maximum value in the range 0° ≤ x ≤ 180°?

  1. A.12½
  2. B.32½
  3. C.57½
  4. D.147½
Show the answer and explanation

Answer: C (57½)

Explanation

Sine is greatest when the angle is 90°: 2x − 25 = 90, so x = 57½.

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Question 37

Trigonometry

From the top of a vertical mast 150m high, two huts on the same ground level are observed. One due East and the other due West of the mast. Their angles of depression are 60° and 45° respectively. Find the distance between the huts.

  1. A.150(1 + √3)m
  2. B.50(3 + √3)m
  3. C.150√3m
  4. D.50/√3m
Show the answer and explanation

Answer: B (50(3 + √3)m)

Explanation

The huts are 150/tan 60° = 50√3 m and 150/tan 45° = 150 m from the mast, on opposite sides. Total = 150 + 50√3 = 50(3 + √3) m.

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Question 38

Differentiation

If y = 243(4x + 5)−2, find dy/dx when x = 1

  1. A.−8/3
  2. B.3/8
  3. C.9/8
  4. D.−8/9
Show the answer and explanation

Answer: A (−8/3)

Explanation

dy/dx = 243 × (−2)(4x + 5)⁻³ × 4. At x = 1: −1944/9³ = −1944/729 = −8/3.

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Question 39

Differentiation

Differentiate x/cos x with respect to x.

  1. A.1 + x sec x tan x
  2. B.1 + sec2x
  3. C.cos x + x tan x
  4. D.sec x + x sec x tan x
Show the answer and explanation

Answer: D (sec x + x sec x tan x)

Explanation

x/cos x = x sec x. By the product rule its derivative is sec x + x sec x tan x.

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Question 40

Integration

Evaluate ∫2π (sec2x − tan2x)dx.

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

Answer: B (π − 2)

Explanation

sec²x − tan²x = 1, so the integral is [x] from 2 to π = π − 2.

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Question 41

Integration

Find the equation of the curve which passes through the point (2, 5) and whose gradient at any point is given by 6x − 5.

  1. A.6x2 − 5x + 5
  2. B.6x2 + 5x + 5
  3. C.3x2 − 5x − 5
  4. D.3x2 − 5x + 3
Show the answer and explanation

Answer: D (3x2 − 5x + 3)

Explanation

Integrating, y = 3x² − 5x + c. At (2, 5): 5 = 12 − 10 + c, so c = 3.

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Question 42

Measures of Central Tendency

If m and n are the mean and median respectively of the set of numbers 2, 3, 9, 7, 6, 7, 8, 5, find m + 2n to the nearest whole number.

  1. A.19
  2. B.18
  3. C.13
  4. D.12
Show the answer and explanation

Answer: A (19)

Explanation

Sum = 47 for 8 numbers, so m = 5.875. In order: 2, 3, 5, 6, 7, 7, 8, 9, so n = (6 + 7)/2 = 6.5. m + 2n = 18.875 ≈ 19.

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Question 43

Measures of Central Tendency

Average hourly earnings (N): 5–9, 10–14, 15–19, 20–24
No. of workers: 17, 32, 25, 24
Estimate the mode of the above frequency distribution.

  1. A.12.2
  2. B.12.7
  3. C.12.9
  4. D.13.4
Show the answer and explanation

Answer: C (12.9)

Explanation

The modal class is 10–14 (32 workers). Mode = L + d₁/(d₁ + d₂) × c = 9.5 + 15/(15 + 7) × 5 ≈ 9.5 + 3.4 = 12.9.

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Question 44

Measures of Dispersion

Find the variance of the number k, k + 1, k + 2

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

Answer: A (2/3)

Explanation

The mean is k + 1 and the deviations are −1, 0, 1. Variance = (1 + 0 + 1)/3 = 2/3.

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Question 45

Measures of Dispersion

Find the positive value of x if the standard deviation of the numbers 1, x + 1, 2x + 1 is √6

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

Answer: C (3)

Explanation

The mean is x + 1 and the deviations are −x, 0, x. Variance = 2x²/3 = 6, so x² = 9 and x = 3.

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Question 46

Probability

A bag contains 16 red and 20 blue balls only. How many white balls must be added to the bag so that the probability of randomly picking a red ball is equal to 2/5?

  1. A.4
  2. B.20
  3. C.24
  4. D.40
Show the answer and explanation

Answer: A (4)

Explanation

We need 16/(36 + w) = 2/5, so 36 + w = 40 and w = 4.

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Question 47

Data Presentation

The pie chart above shows the monthly expenditure of a public servant. The monthly expenditure on housing is twice that of school fees. How much does the worker spend on housing if his monthly income is N7200?

Diagram for this question
  1. A.1000
  2. B.2000
  3. C.3000
  4. D.4000
Show the answer and explanation

Answer: B (2000)

Explanation

Food is 120° and transport 90°, leaving 150° for housing and school fees. Housing is twice school fees, so housing = 100°. 100/360 × 7200 = N2000.

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Question 49

Probability

In a recent zonal championship games involving 10 teams, teams X and Y were given probabilities 2/5 and 1/3 respectively of winning the gold in the football event. What is the probability that either team will win the gold?

  1. A.2/15
  2. B.7/15
  3. C.11/15
  4. D.13/15
Show the answer and explanation

Answer: C (11/15)

Explanation

Only one team can win, so add the probabilities: 2/5 + 1/3 = 6/15 + 5/15 = 11/15.

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Question 50

Probability

If x, y can take values from the set {1, 2, 3, 4}, find the probability that the product of x and y is not greater than 6.

  1. A.5/8
  2. B.5/16
  3. C.1/2
  4. D.7/8
Show the answer and explanation

Answer: A (5/8)

Explanation

There are 4 × 4 = 16 pairs. Products ≤ 6: with x = 1 four pairs, x = 2 three, x = 3 two, x = 4 one, 10 in all. So 10/16 = 5/8.

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