JAMB Mathematics 2008 past questions and answers

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

Question 1

Number Bases

Add 11012, 101112 and 1112

  1. A.1110112
  2. B.1101102
  3. C.1010112
  4. D.1010102
Show the answer and explanation

Answer: C (1010112)

Explanation

In base ten the numbers are 13, 23 and 7, which add to 43 = 32 + 8 + 2 + 1 = 1010112.

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Question 2

Number Bases

If 125x = 2010, find x.

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

Answer: B (3)

Explanation

x2 + 2x + 5 = 20, so x2 + 2x − 15 = 0, (x + 5)(x − 3) = 0 and x = 3 (a base must be positive).

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Question 3

Fractions, Decimals and Approximation

Evaluate (3/8 ÷ 1/2 − 1/3)/(1/8 × 2/3 + 1/3)

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

Answer: D (1)

Explanation

Top: 3/4 − 1/3 = 5/12. Bottom: 1/12 + 1/3 = 5/12. So the value is 1.

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Question 4

Fractions, Decimals and Approximation

Express 123456 to 3 significant figures

  1. A.123 000
  2. B.124 000
  3. C.125 000
  4. D.126 000
Show the answer and explanation

Answer: A (123 000)

Explanation

Keep the first three digits 123; the next digit 4 is less than 5, so round down: 123 000.

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Question 5

Commercial Arithmetic

Calculate the simple interest on N7 500 for 8 years at 5% per annum

  1. A.N3 000
  2. B.N600
  3. C.N300
  4. D.N150
Show the answer and explanation

Answer: A (N3 000)

Explanation

I = PRT/100 = 7500 × 5 × 8/100 = N3 000.

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Question 6

Commercial Arithmetic

The cost of kerosene per litre increases from N60 to N85. What is the percentage rate of increase?

  1. A.42%
  2. B.41%
  3. C.40%
  4. D.25%
Show the answer and explanation

Answer: A (42%)

Explanation

The increase is N25, and 25/60 × 100% ≈ 41.7%, which is 42% to the nearest whole number.

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Question 7

Indices

Simplify 16−½ × 4−½ × 271/3

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

Answer: A (3/8)

Explanation

16−½ = 1/4, 4−½ = 1/2 and 271/3 = 3, so the product is 3/8.

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Question 8

Logarithms

If logx½ 64 = 3, find the value of x.

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

Answer: B (16)

Explanation

(x½)3 = 64, so x3/2 = 64 and x = 642/3 = 16.

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Question 9

Surds

If (1 + √2)/(1 − √2) is expressed in the form x + y√2, find the values of x and y.

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

Answer: A ((−3, −2))

Explanation

Multiply top and bottom by 1 + √2: (1 + √2)2/(1 − 2) = −(3 + 2√2) = −3 − 2√2, so x = −3, y = −2.

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Question 10

Sets

If X = {n2 + 1 : n = 0, 2, 3} and Y = {n + 1 : n = 2, 3, 5}, find X∩Y.

  1. A.{1, 3}
  2. B.{5, 10}
  3. C.Φ
  4. D.{4, 6}
Show the answer and explanation

Answer: C (Φ)

Explanation

X = {1, 5, 10} and Y = {3, 4, 6}. They have no common element, so X ∩ Y is empty.

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Question 11

Sets

A bookseller sells Mathematics and English books. If 30 customers buy Mathematics books, 20 customers buy English books and 10 customers buy the two books, how many customers has he altogether?

  1. A.30
  2. B.40
  3. C.50
  4. D.60
Show the answer and explanation

Answer: B (40)

Explanation

Total = 30 + 20 − 10 = 40 (the 10 who bought both were counted twice).

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Question 12

Algebraic Expressions

Make Q the subject of the formula when L = (4/3)M√(PQ)

  1. A.9L2/16M2P
  2. B.3L/4M√P
  3. C.√(3L)/4MP
  4. D.3L2/16M2P
Show the answer and explanation

Answer: A (9L2/16M2P)

Explanation

√(PQ) = 3L/(4M). Squaring, PQ = 9L2/(16M2), so Q = 9L2/(16M2P).

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Question 13

Polynomials

If 2x2 − kx − 12 is divisible by x − 4, find the value of k.

  1. A.4
  2. B.5
  3. C.6
  4. D.7
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Answer: B (5)

Explanation

By the factor theorem, x = 4 gives zero: 32 − 4k − 12 = 0, so k = 5.

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Question 14

Algebraic Expressions

Factorize completely (4x + 3y)2 − (3x − 2y)2

  1. A.(x + 5y)(7x + y)
  2. B.(x + 5y)(7x − y)
  3. C.(x − 5y)(7x + y)
  4. D.(x − 5y)(7x − y)
Show the answer and explanation

Answer: A ((x + 5y)(7x + y))

Explanation

Difference of two squares: (4x + 3y − 3x + 2y)(4x + 3y + 3x − 2y) = (x + 5y)(7x + y).

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Question 15

Variation

If x − 3 is directly proportional to the square of y and x = 5 when y = 2, find x when y = 6.

  1. A.30
  2. B.21
  3. C.16
  4. D.12
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Answer: B (21)

Explanation

x − 3 = ky2: 2 = 4k, so k = ½. When y = 6, x − 3 = 18 and x = 21.

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Question 16

Variation

If p varies inversely as the square of q and p = 8 when q = 4, find q when p = 32.

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

Answer: D (±2)

Explanation

p = k/q2: k = 8 × 16 = 128. Then q2 = 128/32 = 4, so q = ±2.

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Question 17

Inequalities

Find the range of values of x which satisfy the inequalities 4x − 7 ≤ 3x and 3x − 4 ≤ 4x.

  1. A.−4 ≤ x ≤ 7
  2. B.−7 ≤ x ≤ 4
  3. C.x ≥ −7
  4. D.−7 ≤ x ≤ 6
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Answer: A (−4 ≤ x ≤ 7)

Explanation

4x − 7 ≤ 3x gives x ≤ 7, and 3x − 4 ≤ 4x gives x ≥ −4. Together −4 ≤ x ≤ 7.

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Question 18

Inequalities

Solve the quadratic inequality x2 − 5x + 6 ≥ 0

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

Answer: A (x ≤ 2, x ≥ 3)

Explanation

x2 − 5x + 6 = (x − 2)(x − 3), which is zero at 2 and 3 and positive outside them: x ≤ 2 or x ≥ 3.

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Question 19

Inequalities

The shaded area that gives the solution set for the inequalities x + y ≤ 3, x − y ≤ 3, is

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

Answer: B (Graph B)

Explanation

x + y ≤ 3 is on or below the line through (0, 3) and (3, 0); x − y ≤ 3 is on or above the line through (3, 0) and (0, −3). The region between both lines, left of (3, 0), is the one shaded in B.

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Question 20

Progressions

The fifth term of an A.P. is 24 and the eleventh term is 96. Find the first term.

  1. A.12
  2. B.4
  3. C.−12
  4. D.−24
Show the answer and explanation

Answer: D (−24)

Explanation

a + 4d = 24 and a + 10d = 96, so 6d = 72, d = 12 and a = 24 − 48 = −24.

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Question 21

Binary Operations

A binary operation * defined on the set of positive integers is such that x * y = 2x − 3y + 2 for all positive integers x and y. The binary operation is

  1. A.commutative and closed on the set of positive integers
  2. B.neither commutative nor closed on the set of positive integers
  3. C.commutative but not closed on the set of positive integers
  4. D.not commutative but closed on the set of positive integers.
Show the answer and explanation

Answer: B (neither commutative nor closed on the set of positive integers)

Explanation

y * x = 2y − 3x + 2 is different from x * y, so it is not commutative. 1 * 2 = 2 − 6 + 2 = −2 is not a positive integer, so it is not closed.

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Question 22

Binary Operations

A binary operation on the set of real numbers excluding −1 is such that for all m, n ∈ R, m Δ n = m + n + mn. Find the identity element of the operation.

  1. A.1
  2. B.0
  3. C.−½
  4. D.−1
Show the answer and explanation

Answer: B (0)

Explanation

m Δ e = m gives m + e + me = m, so e(1 + m) = 0 and e = 0.

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Question 23

Matrices and Determinants

Find the values of x and y respectively if (1 0; −1 −1; 2 2) + (x 1; −1 0; y −2) = (−2 1; −2 −1; −3 0) (matrices written row by row)

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

Answer: D (−3, −5)

Explanation

Top-left: 1 + x = −2, so x = −3. Bottom-left: 2 + y = −3, so y = −5.

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Question 24

Matrices and Determinants

If (−2 1; 2 3)(p q; r s) = (1 0; 0 1), what is the value of r? (Matrices written row by row.)

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

Answer: D (1/4)

Explanation

(p q; r s) is the inverse of (−2 1; 2 3). The determinant is −6 − 2 = −8, so r = −2/(−8) = 1/4.

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Question 25

Angles and Polygons

In the diagram above, PQ//RS. The size of the angle marked x is

Diagram for this question
  1. A.100°
  2. B.80°
  3. C.50°
  4. D.30°
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Answer: B (80°)

Explanation

The two slanting lines and PQ form a triangle with interior angles 50° and 30°. x is the exterior angle at the third corner, so x = 50° + 30° = 80°.

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Question 26

Angles and Polygons

Find the exterior angle of a 12 sided regular polygon.

  1. A.12°
  2. B.24°
  3. C.25°
  4. D.30°
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Answer: D (30°)

Explanation

Each exterior angle = 360° ÷ 12 = 30°.

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Question 27

Triangles and Quadrilaterals

In the diagram above, ∠OPQ is

Diagram for this question
  1. A.90°
  2. B.53°
  3. C.36°
  4. D.26°
Show the answer and explanation

Answer: B (53°)

Explanation

OP = OQ (radii), so the base angles are equal: ∠OPQ = (180° − 74°)/2 = 53°.

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Question 28

Mensuration of Plane Shapes

Find the area of the figure above. [π = 22/7]

Diagram for this question
  1. A.12.5cm2
  2. B.75.0cm2
  3. C.78.5cm2
  4. D.84.8cm2
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Answer: D (84.8cm2)

Explanation

Rectangle = 5 × 15 = 75cm2. Semicircle of radius 2.5cm = ½ × 22/7 × 6.25 ≈ 9.8cm2. Total ≈ 84.8cm2.

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Question 29

Circle Theorems

Find the angle subtended at the centre of a circle by a chord which is equal in length to the radius of the circle.

  1. A.30°
  2. B.45°
  3. C.60°
  4. D.90°
Show the answer and explanation

Answer: C (60°)

Explanation

The chord and the two radii form an equilateral triangle, so the angle at the centre is 60°.

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Question 32

Coordinate Geometry

Find the gradient of the line which is perpendicular to the line with the equation 3x + 2y + 1 = 0

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

Answer: B (2/3)

Explanation

2y = −3x − 1, so the line has gradient −3/2. The perpendicular gradient is the negative reciprocal, 2/3.

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Question 33

Coordinate Geometry

Calculate the distance between points L(−1, −6) and M(−3, −5)

  1. A.√5
  2. B.2√3
  3. C.√20
  4. D.√53
Show the answer and explanation

Answer: A (√5)

Explanation

d = √((−3 + 1)2 + (−5 + 6)2) = √(4 + 1) = √5.

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Question 34

Trigonometry

If sin θ = 3/5, find tan θ.

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

Answer: A (3/4)

Explanation

With opposite 3 and hypotenuse 5, the adjacent side is 4, so tan θ = 3/4.

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Question 35

Trigonometry

A student sitting on a tower 68 metres high observes his principal's car at an angle of depression of 20°. How far is the car from the bottom of the tower to the nearest metre?

  1. A.184m
  2. B.185m
  3. C.186m
  4. D.187m
Show the answer and explanation

Answer: D (187m)

Explanation

Distance = 68/tan 20° = 68/0.364 ≈ 186.8m, which is 187m to the nearest metre.

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Question 36

Differentiation

Find the derivative of y = (x7 − x5)/x4.

  1. A.x(x2 − 1)
  2. B.3x(x2 − 1)
  3. C.3x2 − 1
  4. D.7x6 − 5x4
Show the answer and explanation

Answer: C (3x2 − 1)

Explanation

Simplify first: y = x3 − x, so dy/dx = 3x2 − 1.

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Question 37

Differentiation

Differentiate sin x − x cos x.

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

Answer: B (x sin x)

Explanation

d/dx(sin x) = cos x and d/dx(x cos x) = cos x − x sin x. So the derivative is cos x − cos x + x sin x = x sin x.

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Question 38

Differentiation

Find the minimum value of the function y = x(1 + x)

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

Answer: A (−1/4)

Explanation

dy/dx = 1 + 2x = 0 at x = −½. The minimum value is y = −½ × ½ = −¼.

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Question 39

Integration

Evaluate ∫12 (6x2 − 2x) dx.

  1. A.16
  2. B.13
  3. C.12
  4. D.11
Show the answer and explanation

Answer: D (11)

Explanation

[2x3 − x2] from 1 to 2 = (16 − 4) − (2 − 1) = 11.

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Question 40

Integration

Evaluate ∫−π/2π/2 cos x dx.

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

Answer: C (2)

Explanation

[sin x] from −π/2 to π/2 = 1 − (−1) = 2.

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Question 41

Data Presentation

On a pie chart, there are six sectors of which four angles are 30°, 45°, 60°, 90° and the remaining two angles are in the ratio 2:1. Find the smaller angles of the remaining two angles.

  1. A.15°
  2. B.30°
  3. C.45°
  4. D.60°
Show the answer and explanation

Answer: C (45°)

Explanation

The remaining angles total 360° − 225° = 135°, split 2 : 1 as 90° and 45°. The smaller is 45°.

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Question 42

Data Presentation

The bar chart above shows the number of times the words a, and, in, it, the, to appear in a paragraph in a book. What is the ratio of the least frequent word to that of the most frequent word?

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

Answer: A (1/4)

Explanation

The shortest bar ("and") is about 3 and the tallest ("the") is about 12, giving 3 : 12 = 1/4.

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Question 43

Measures of Central Tendency

What is the mean of the data t, 2t − 1, t − 2, 2t − 1, 4t and 2t + 2?

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

Answer: D (2t − 1/3)

Explanation

The sum is 12t − 2 and there are 6 values, so the mean is (12t − 2)/6 = 2t − 1/3.

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Question 44

Measures of Central Tendency

Find the median of 4, 1, 4, 1, 0, 4, 4, 2 and 0.

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

Answer: C (2)

Explanation

In order: 0, 0, 1, 1, 2, 4, 4, 4, 4. The middle (5th) value is 2.

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Question 45

Measures of Dispersion

If x > 0, find the range of the numbers x − 3, 3x + 2, x − 1, 4x, 2x − 1, x − 2, 2x − 2, 3x and 3x + 1.

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

Answer: A (3x + 3)

Explanation

For x > 0 the largest is 4x and the smallest is x − 3, so the range is 4x − (x − 3) = 3x + 3.

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Question 47

Permutation and Combination

In how many ways can the letters of the word ACCEPTANCE be arranged?

  1. A.10!/(2! 2! 3!)
  2. B.10!/(2! 3!)
  3. C.10!/(2! 2!)
  4. D.10!
Show the answer and explanation

Answer: A (10!/(2! 2! 3!))

Explanation

There are 10 letters with A twice, C three times and E twice, so the number of arrangements is 10!/(2! 3! 2!).

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Question 48

Permutation and Combination

Find the number of ways of selecting 6 out of 10 subjects for an examination.

  1. A.218
  2. B.216
  3. C.215
  4. D.210
Show the answer and explanation

Answer: D (210)

Explanation

10C6 = 10C4 = 210.

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Question 49

Probability

The probability of picking a letter T from the word OBSTRUCTION is

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

Answer: B (2/11)

Explanation

OBSTRUCTION has 11 letters, and 2 of them are T, so the probability is 2/11.

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Question 50

Probability

The result of rolling a fair die 150 times is summarized in the table below.
Number: 1, 2, 3, 4, 5, 6
Frequency: 12, 18, x, 30, 2x, 45
What is the probability of obtaining a 5?

  1. A.3/10
  2. B.1/5
  3. C.1/6
  4. D.1/10
Show the answer and explanation

Answer: B (1/5)

Explanation

12 + 18 + x + 30 + 2x + 45 = 150 gives 3x = 45 and x = 15. A 5 came up 2x = 30 times, so P = 30/150 = 1/5.

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