JAMB Mathematics 2012 past questions and answers

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

Question 2

Number Bases

Convert 726 to a number in base three.

  1. A.2211
  2. B.2121
  3. C.1212
  4. D.1122
Show the answer and explanation

Answer: D (1122)

Explanation

726 = 7 × 6 + 2 = 44. Dividing 44 repeatedly by 3 gives remainders 2, 2, 1, 1, so 44 = 11223.

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Question 3

Fractions, Decimals and Approximation

Simplify (2⅔ × 1½)/4⅘

  1. A.1¼
  2. B.1 1/6
  3. C.5/6
  4. D.4/5
Show the answer and explanation

Answer: C (5/6)

Explanation

2⅔ × 1½ = 8/3 × 3/2 = 4, and 4 ÷ 24/5 = 4 × 5/24 = 5/6.

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Question 4

Fractions, Decimals and Approximation

Evaluate 21/9 to 3 significant figures.

  1. A.2.30
  2. B.2.31
  3. C.2.32
  4. D.2.33
Show the answer and explanation

Answer: D (2.33)

Explanation

21 ÷ 9 = 2.333..., which is 2.33 to 3 significant figures.

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Question 5

Commercial Arithmetic

A man earns N3 500 per month out of which he spends 15% on his children's education. If he spends additional N1 950 on food, how much does he have left?

  1. A.N525
  2. B.N1 025
  3. C.N1 950
  4. D.N2 975
Show the answer and explanation

Answer: B (N1 025)

Explanation

Education costs 15% of 3500 = N525. With N1,950 on food he spends N2,475, leaving 3500 − 2475 = N1,025.

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Question 7

Logarithms

If log3x2 = −8, what is x?

  1. A.1/3
  2. B.1/9
  3. C.1/27
  4. D.1/81
Show the answer and explanation

Answer: D (1/81)

Explanation

x2 = 3−8, so x = 3−4 = 1/81.

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Question 8

Surds

Simplify (√6 + 2)2 − (√6 − 2)2

  1. A.2√6
  2. B.4√6
  3. C.8√6
  4. D.16√6
Show the answer and explanation

Answer: C (8√6)

Explanation

Difference of two squares: [(√6 + 2) + (√6 − 2)][(√6 + 2) − (√6 − 2)] = 2√6 × 4 = 8√6.

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Question 9

Sets

If P is a set of all prime factors of 30 and Q is a set of all factors of 18 less than 10, find P∩Q.

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

Answer: B ({2,3})

Explanation

P = {2, 3, 5} and Q = {1, 2, 3, 6, 9}. The common elements are 2 and 3.

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Question 10

Sets

In a class of 46 students, 22 play football and 26 play volleyball. If 3 students play both games how many play neither?

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

Answer: A (1)

Explanation

At least one game: 22 + 26 − 3 = 45. Neither: 46 − 45 = 1.

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Question 11

Algebraic Expressions

Make n the subject of the formula if w = v(2 + cn)/(1 − cn)

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

Answer: A ((1/c)((w − 2v)/(v + w)))

Explanation

w − cnw = 2v + cnv, so w − 2v = cn(v + w) and n = (w − 2v)/(c(v + w)).

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Question 12

Polynomials

Find the remainder when 2x3 − 11x2 + 8x − 1 is divided by x + 3.

  1. A.−871
  2. B.−781
  3. C.−187
  4. D.−178
Show the answer and explanation

Answer: D (−178)

Explanation

Put x = −3: 2(−27) − 11(9) + 8(−3) − 1 = −54 − 99 − 24 − 1 = −178.

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Question 13

Linear and Simultaneous Equations

Solve for x and y in the equations below.
x2 − y2 = 4
x + y = 2

  1. A.x = 0, y = −2
  2. B.x = 0, y = 2
  3. C.x = 2, y = 0
  4. D.x = −2, y = 0
Show the answer and explanation

Answer: C (x = 2, y = 0)

Explanation

x2 − y2 = (x + y)(x − y), so 2(x − y) = 4 and x − y = 2. With x + y = 2, x = 2 and y = 0.

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Question 14

Variation

If y varies directly as √n and y = 4 when n = 4, find y when n = 1 7/9.

  1. A.√17
  2. B.4/3
  3. C.8/3
  4. D.2/3
Show the answer and explanation

Answer: C (8/3)

Explanation

y = k√n: 4 = 2k, so k = 2. n = 16/9 gives √n = 4/3, so y = 8/3.

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Question 15

Variation

U is inversely proportional to the cube of V and U = 81 when V = 2. Find U when V = 3.

  1. A.24
  2. B.27
  3. C.32
  4. D.36
Show the answer and explanation

Answer: A (24)

Explanation

U = k/V3: k = 81 × 8 = 648. When V = 3, U = 648/27 = 24.

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Question 16

Inequalities

The value of y for which (1/5)y + 1/5 < (1/2)y + 2/5 is

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

Answer: C (y > −2/3)

Explanation

Multiply by 10: 2y + 2 < 5y + 4, so −3y < 2 and y > −2/3.

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Question 17

Inequalities

Find the range of values of m which satisfy (m − 3)(m − 4) < 0.

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

Answer: C (3 < m < 4)

Explanation

The product of (m − 3) and (m − 4) is negative only when m lies between the roots 3 and 4.

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Question 18

Inequalities

The shaded region above is represented by the equation

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

Answer: C (y ≤ −4x + 4)

Explanation

The line through (0, 4) and (1, 0) is y = −4x + 4. The region on the origin side is below it, so y ≤ −4x + 4.

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Question 19

Progressions

The nth term of a sequence is n2 − 6n − 4. Find the sum of the 3rd and 4th terms.

  1. A.24
  2. B.23
  3. C.−24
  4. D.−25
Show the answer and explanation

Answer: D (−25)

Explanation

T3 = 9 − 18 − 4 = −13 and T4 = 16 − 24 − 4 = −12, so the sum is −25.

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Question 20

Progressions

The sum to infinity of a geometric progression is −1/10 and the first term is −1/8. Find the common ratio of the progression.

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

Answer: B (−1/4)

Explanation

−1/10 = (−1/8)/(1 − r), so 1 − r = 10/8 and r = −1/4.

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Question 21

Binary Operations

The binary operation * is defined on the set of integers such that p * q = pq + p − q. Find 2*(3*4).

  1. A.11
  2. B.13
  3. C.15
  4. D.22
Show the answer and explanation

Answer: B (13)

Explanation

3 * 4 = 12 + 3 − 4 = 11. Then 2 * 11 = 22 + 2 − 11 = 13.

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Question 22

Binary Operations

A binary operation on the set of real numbers is defined by m * n = mn/2 for all m, n ∈ R. If the identity element is 2, find the inverse of −5.

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

Answer: A (−4/5)

Explanation

The inverse a satisfies −5a/2 = 2, so a = −4/5.

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Question 24

Matrices and Determinants

Given that I3 is a unit matrix of order 3, find |I3|.

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

Answer: C (1)

Explanation

The unit matrix has 1s on the diagonal and 0s elsewhere, so its determinant is 1 × 1 × 1 = 1.

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Question 25

Angles and Polygons

In the diagram above, QR//TU, ∠PQR = 80° and ∠PSU = 95°. Calculate ∠SUT.

Diagram for this question
  1. A.15°
  2. B.25°
  3. C.30°
  4. D.80°
Show the answer and explanation

Answer: A (15°)

Explanation

∠STU = ∠PQR = 80° (corresponding angles) and ∠TSU = 180° − 95° = 85°. In triangle STU, x = 180° − 80° − 85° = 15°.

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Question 26

Angles and Polygons

The angles of a polygon are given by x, 2x, 3x, 4x and 5x respectively. Find the value of x.

  1. A.24°
  2. B.30°
  3. C.33°
  4. D.36°
Show the answer and explanation

Answer: D (36°)

Explanation

Five angles make a pentagon, whose angles add to 540°: 15x = 540, so x = 36°.

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Question 27

Circle Theorems

In the diagram above, PQR is a circle centre O. If ∠QPR is x°, find ∠QRP.

Diagram for this question
  1. A.x°
  2. B.(90 − x)°
  3. C.(90 + x)°
  4. D.(180 − x)°
Show the answer and explanation

Answer: B ((90 − x)°)

Explanation

PR passes through O, so it is a diameter and ∠PQR = 90°. The angles of triangle PQR add to 180°, so ∠QRP = 90° − x.

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Question 28

Mensuration of Plane Shapes

Find the area of the trapezium above.

Diagram for this question
  1. A.91 cm2
  2. B.78 cm2
  3. C.60 cm2
  4. D.19 cm2
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Answer: C (60 cm2)

Explanation

Area = ½ × (7 + 13) × 6 = 60 cm2.

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Question 29

Mensuration of Plane Shapes

A circular arc subtends angle 150° at the centre of a circle of radius 12 cm. Calculate the area of the sector of the arc.

  1. A.30π cm2
  2. B.60π cm2
  3. C.120π cm2
  4. D.150π cm2
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Answer: B (60π cm2)

Explanation

Area = 150/360 × π × 144 = 60π cm2.

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Question 30

Mensuration of Solids

Calculate the volume of a cuboid of length 0.76 cm, breadth 2.6 cm and height 0.82cm.

  1. A.3.92 cm3
  2. B.2.13 cm3
  3. C.1.97 cm3
  4. D.1.62 cm3
Show the answer and explanation

Answer: D (1.62 cm3)

Explanation

Volume = 0.76 × 2.6 × 0.82 ≈ 1.62 cm3.

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Question 31

Loci

The locus of a point equidistant from the intersection of lines 3x − 7y + 7 = 0 and 4x − 6y + 1 = 0 is a

  1. A.line parallel to 7x + 13y + 8 = 0
  2. B.circle
  3. C.semicircle
  4. D.bisector of the line 7x + 13y + 8 = 0.
Show the answer and explanation

Answer: B (circle)

Explanation

Points at a fixed distance from one point (here the intersection of the two lines) form a circle centred at that point.

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Question 32

Coordinate Geometry

The gradient of the straight line joining the points P(5,−7) and Q(−2,−3) is

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

Answer: C (−4/7)

Explanation

Gradient = (−3 + 7)/(−2 − 5) = 4/(−7) = −4/7.

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Question 33

Coordinate Geometry

The distance between the point (4,3) and the intersection of y = 2x + 4 and y = 7 − x is

  1. A.√13
  2. B.3√2
  3. C.√26
  4. D.10√5
Show the answer and explanation

Answer: B (3√2)

Explanation

2x + 4 = 7 − x gives x = 1, y = 6. Distance from (4, 3) = √(32 + 32) = √18 = 3√2.

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Question 34

Coordinate Geometry

Find the equation of the line through the points (−2,1) and (−½,4).

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

Answer: B (y = 2x + 5)

Explanation

Gradient = (4 − 1)/(−½ + 2) = 3/1.5 = 2. Then y − 1 = 2(x + 2), so y = 2x + 5.

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Question 35

Trigonometry

If angle θ is 135°, evaluate cos θ.

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

Answer: C (−√2/2)

Explanation

cos 135° = −cos 45° = −√2/2.

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Question 36

Trigonometry

A man stands on a tree 150 cm high and sees a boat at an angle of depression of 74°. Find the distance of the boat from the base of the tree.

  1. A.52cm
  2. B.43cm
  3. C.40cm
  4. D.15cm
Show the answer and explanation

Answer: B (43cm)

Explanation

The angle of elevation from the boat is 74°, so distance = 150/tan 74° ≈ 150/3.487 ≈ 43cm.

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Question 38

Differentiation

Find dy/dx if y = cos x.

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

Answer: B (−sin x)

Explanation

The derivative of cos x is −sin x.

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Question 39

Integration

Evaluate ∫12 (x2 − 4x) dx

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

Answer: D (−11/3)

Explanation

[x3/3 − 2x2] from 1 to 2 = (8/3 − 8) − (1/3 − 2) = 7/3 − 6 = −11/3.

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Question 40

Integration

Evaluate ∫0π/4 sec2θ dθ

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

Answer: A (1)

Explanation

∫sec2θ dθ = tan θ. From 0 to π/4: tan 45° − tan 0 = 1.

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Question 42

Data Presentation

The bar chart above shows the distribution of marks in a class test. If the pass mark is 5, what percentage of the students failed the test?

Diagram for this question
  1. A.10%
  2. B.20%
  3. C.50%
  4. D.60%
Show the answer and explanation

Answer: C (50%)

Explanation

The bars total 40 students. Those scoring below 5 (marks 0 to 4) number 2 + 3 + 4 + 6 + 5 = 20, which is 50%.

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Question 43

Measures of Central Tendency

The mean of seven numbers is 96. If an eighth number is added, the mean becomes 112. Find the eighth number.

  1. A.126
  2. B.180
  3. C.216
  4. D.224
Show the answer and explanation

Answer: D (224)

Explanation

The seven numbers total 672 and the eight total 896, so the eighth number is 224.

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Question 44

Measures of Central Tendency

Find the median of 2,3,7,3,4,5,8,9,9,4,5,3,4,2,4 and 5.

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

Answer: D (4)

Explanation

In order: 2, 2, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 7, 8, 9, 9. The 8th and 9th values are both 4, so the median is 4.

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Question 45

Measures of Dispersion

Find the range of 4,9,6,3,2,8,10 and 11.

  1. A.11
  2. B.9
  3. C.8
  4. D.4
Show the answer and explanation

Answer: B (9)

Explanation

Range = 11 − 2 = 9.

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Question 47

Permutation and Combination

Evaluate n+1Cn−2 if n = 15.

  1. A.3630
  2. B.3360
  3. C.1120
  4. D.560
Show the answer and explanation

Answer: D (560)

Explanation

16C13 = 16C3 = (16 × 15 × 14)/6 = 560.

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Question 48

Permutation and Combination

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

  1. A.6720
  2. B.6270
  3. C.6207
  4. D.6027
Show the answer and explanation

Answer: A (6720)

Explanation

TOTALITY has 8 letters with T three times, so 8!/3! = 40320/6 = 6720.

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Question 49

Probability

The probability that a student passes a Physics test is 2/3. If he takes three Physics tests, what is the probability that he passes two of the tests?

  1. A.4/9
  2. B.6/9
  3. C.4/27
  4. D.2/27
Show the answer and explanation

Answer: A (4/9)

Explanation

Exactly two passes can happen in 3 orders, each with probability (2/3)(2/3)(1/3) = 4/27. Total = 3 × 4/27 = 4/9.

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Question 50

Probability

The probabilities that a man and his wife live for 80 years are 2/3 and 3/5 respectively. Find the probability that at least one of them will live up to 80 years.

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

Answer: D (13/15)

Explanation

P(neither) = 1/3 × 2/5 = 2/15, so P(at least one) = 1 − 2/15 = 13/15.

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