JAMB Mathematics 1980 past questions and answers

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

Question 1

Fractions, Decimals and Approximation

Find correct to three significant figures, the value of √(41830)

  1. A.205
  2. B.647
  3. C.2050
  4. D.6470
  5. E.64.7
Show the answer and explanation

Answer: A (205)

Explanation

200² = 40000 and 205² = 42025, so √41830 ≈ 204.5, which is 205 to three significant figures.

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Question 2

Indices

Evaluate (20 + 4-½)2

  1. A.1/4
  2. B.5/4
  3. C.9/4
  4. D.4
  5. E.9
Show the answer and explanation

Answer: C (9/4)

Explanation

2⁰ = 1 and 4^(−½) = 1/√4 = ½, so the value is (1½)² = 9/4.

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Question 3

Fractions, Decimals and Approximation

Which of the following is NOT a factor of 124 − 54?

  1. A.7
  2. B.13
  3. C.17
  4. D.49
  5. E.169.
Show the answer and explanation

Answer: D (49)

Explanation

12⁴ − 5⁴ = (144 + 25)(144 − 25) = 169 × 119 = 13² × 7 × 17. It contains only one 7, so 49 is not a factor.

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Question 4

Surds

Rationalize the denominator of the given expression (√(1 + a) − √a)/(√(1 + a) + √a)

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

Answer: A (1 + 2a − 2√(a(1 + a)))

Explanation

Multiply top and bottom by √(1 + a) − √a. The bottom becomes (1 + a) − a = 1 and the top (√(1 + a) − √a)² = 1 + 2a − 2√(a(1 + a)).

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Question 5

Commercial Arithmetic

When a dealer sells a bicycle for ₦81 he makes a profit of 8%. What did he pay for the bicycle?

  1. A.₦73
  2. B.₦74.52
  3. C.₦75
  4. D.₦75.52
  5. E.₦87.48.
Show the answer and explanation

Answer: C (₦75)

Explanation

₦81 is 108% of the cost price, so the cost is 81 × 100/108 = ₦75.

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Question 6

Measures of Central Tendency

The median of the set of numbers 4, 9, 4, 13, 7, 14, 10, 17 is

  1. A.13
  2. B.7
  3. C.19/2
  4. D.10
  5. E.39/4
Show the answer and explanation

Answer: C (19/2)

Explanation

In order: 4, 4, 7, 9, 10, 13, 14, 17. With eight numbers the median is the average of the 4th and 5th: (9 + 10)/2 = 19/2.

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Question 7

Inequalities

List all integer values of x satisfying the inequality −1 < 2x − 5 ≤ 5

  1. A.2, 3, 4, 5
  2. B.2, 5
  3. C.3, 4, 5
  4. D.2, 3, 4
  5. E.3.1.
Show the answer and explanation

Answer: C (3, 4, 5)

Explanation

Add 5: 4 < 2x ≤ 10, so 2 < x ≤ 5. The integers are 3, 4 and 5.

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Question 8

Quadratic Equations

Find the roots of the equation 10x2 − 13x − 3 = 0

  1. A.x = 3/5 or −1/3
  2. B.x = 3/10 or −1
  3. C.x = −3/10 or 1
  4. D.x = 1/5 or −3/2
  5. E.x = −1/5 or 3/2
Show the answer and explanation

Answer: E (x = −1/5 or 3/2)

Explanation

10x² − 13x − 3 = (5x + 1)(2x − 3) = 0, so x = −1/5 or 3/2.

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Question 9

Mensuration of Solids

A solid cylinder of radius 3cm has a total surface area of 36πcm2. Find its height

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

Answer: B (3cm)

Explanation

Total surface area = 2πr² + 2πrh = 18π + 6πh = 36π, so 6πh = 18π and h = 3cm.

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Question 10

Trigonometry

If PN is perpendicular to QR, find the value of tan x

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

Answer: B (3/5)

Explanation

In triangle PQN, QN = √(5² − 3²) = 4cm, so NR = 9 − 4 = 5cm. tan x = PN/NR = 3/5.

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Question 11

Triangles and Quadrilaterals

In the figure below, PQ∥SR, ST∥RQ, PS = 7cm, PT = 7cm, SR = 4cm. Find the ratio of the area of QRST to the area of PQRS.

Diagram for this question
  1. A.56:77
  2. B.56:105
  3. C.28:105
  4. D.28:49
  5. E.56:49
Show the answer and explanation

Answer: B (56:105)

Explanation

QRST is a parallelogram with base 4cm and height 7cm: area 28cm². PQ = 7 + 4 = 11cm, so trapezium PQRS = ½(11 + 4) × 7 = 52.5cm². 28 : 52.5 = 56 : 105.

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Question 12

Angles and Polygons

In the figure below, if PT is parallel to RS, PQ = PT and angle SQT = 90°, find x

Diagram for this question
  1. A.35°
  2. B.50°
  3. C.55°
  4. D.70°
  5. E.80°.
Show the answer and explanation

Answer: D (70°)

Explanation

Let <PQT = <PTQ = y (isosceles). PT ∥ RS makes <P + x = 180°, so x = 2y. On the line at Q, <SQR = 90° − y, and in triangle QSR, 55° + x + 90° − y = 180°. So y = 35° and x = 70°.

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Question 13

Fractions, Decimals and Approximation

Write down the number 0.0052048 correct to three significant figures.

  1. A.0.005
  2. B.0.0052
  3. C.0.00520
  4. D.5.2048
  5. E.5204.
Show the answer and explanation

Answer: C (0.00520)

Explanation

The first significant figure is 5; keeping three (5, 2, 0) and rounding the next digit 4 down gives 0.00520.

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Question 14

Triangles and Quadrilaterals

In the figure below PS bisects angle QPR. Find the ratio SR:QR

Diagram for this question
  1. A.1:2
  2. B.1:3
  3. C.1:4
  4. D.1:5
  5. E.1:6
Show the answer and explanation

Answer: D (1:5)

Explanation

The angle bisector divides the opposite side in the ratio of the other two sides: QS : SR = PQ : PR = 4 : 1. So SR is 1 part out of 5 and SR : QR = 1 : 5.

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Question 15

Triangles and Quadrilaterals

The ratio of the areas of similar triangles is necessarily equal to

  1. A.the ratio of the corresponding sides
  2. B.the ratio of the squares on corresponding sides
  3. C.the ratio of the corresponding heights of the triangles
  4. D.half the ratio of the corresponding heights of the triangles
  5. E.the ratio of the corresponding bases to the heights of the triangles.
Show the answer and explanation

Answer: B (the ratio of the squares on corresponding sides)

Explanation

If the sides are in the ratio k, every length scales by k and areas scale by k², the ratio of the squares on corresponding sides.

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Question 16

Loci

P and Q are fixed points and X is a variable point which moves so that angle PXQ = 45°. What is the locus of X?

  1. A.A pair of straight lines parallel to PQ
  2. B.The perpendicular bisector of PQ
  3. C.An arc of a circle passing through P and Q
  4. D.A circle with diameter PQ.
  5. E.The bisector of angle PXQ.
Show the answer and explanation

Answer: C (An arc of a circle passing through P and Q)

Explanation

Angles in the same segment of a circle are equal, so all points where PQ subtends 45° lie on an arc of a circle through P and Q.

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Question 17

Commercial Arithmetic

A man and wife went to buy an article costing ₦400. The woman had 10% of the cost and the man 40% of the remainder. How much did they have altogether?

  1. A.₦216
  2. B.₦200
  3. C.₦184
  4. D.₦144.
  5. E.₦100.
Show the answer and explanation

Answer: C (₦184)

Explanation

The woman had 10% of 400 = ₦40. The remainder is ₦360 and the man had 40% of it = ₦144. Together ₦184.

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Question 18

Logarithms

Simplify log108/log104

  1. A.log102
  2. B.log104
  3. C.3/2
  4. D.2
  5. E.None of the above.
Show the answer and explanation

Answer: C (3/2)

Explanation

log 8 = 3 log 2 and log 4 = 2 log 2, so the quotient is 3/2.

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Question 19

Algebraic Expressions

Make c the subject of the formula v = 1 − (a/5)(b + 3/7c)

  1. A.c = −[7b/3 + (5/a)(v − 1)]
  2. B.c = −(7/3)[b + (5/a)(v − 1)]
  3. C.c = (7/3)[b + (5/a)(v − 1)]
  4. D.c = −(7/3)[b + (5v − 1)/a]
  5. E.c = (7/3)[b − (5/a)(v − 1)]
Show the answer and explanation

Answer: B (c = −(7/3)[b + (5/a)(v − 1)])

Explanation

v − 1 = −(a/5)(b + 3c/7), so b + 3c/7 = −5(v − 1)/a. Then 3c/7 = −[b + (5/a)(v − 1)] and c = −(7/3)[b + (5/a)(v − 1)].

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Question 20

Algebraic Expressions

What factor is common to all the expressions x2 − x, 2x2 + x − 1 and x2 − 1?

  1. A.x
  2. B.x − 1
  3. C.x + 1
  4. D.No common factor
  5. E.(2x − 1).
Show the answer and explanation

Answer: D (No common factor)

Explanation

x² − x = x(x − 1), 2x² + x − 1 = (2x − 1)(x + 1) and x² − 1 = (x + 1)(x − 1). No single factor appears in all three.

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Question 21

Progressions

Which of the formulae below represents the general terms of the following set of numbers {−1, 2/3, −1/2, 2/5, …} for n = 1, 2, 3, 4, …?

  1. A.2/(n + 1)
  2. B.(−1)n + 1 × 2/(n + 1)
  3. C.(−1)n × 2/(n + 1)
  4. D.n/(2n − 1)
  5. E.(−1)n × n/(2n + 1)
Show the answer and explanation

Answer: C ((−1)n × 2/(n + 1))

Explanation

The terms are 2/2, 2/3, 2/4, 2/5 with signs −, +, −, +. The sign is (−1)ⁿ, so the nth term is (−1)ⁿ × 2/(n + 1).

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Question 22

Linear and Simultaneous Equations

Three numbers, x, y and z, are connected by the relationships y = 4/9x + 1 and z = 4/9y + 1. If x = 99 find z

  1. A.6⅓
  2. B.20
  3. C.21
  4. D.1764/9
  5. E.None of the above.
Show the answer and explanation

Answer: C (21)

Explanation

y = 4/9 × 99 + 1 = 45, then z = 4/9 × 45 + 1 = 21.

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Question 23

Measures of Central Tendency

In a school there are 35 students in Class 2A and 40 in Class 2B. The mean score for Class 2A in an English Literature examination is 60.0 and that for 2B in the same paper is 52.5. Find, to one place of decimal, the mean for the combined classes.

  1. A.1.5
  2. B.56.0
  3. C.56.2
  4. D.56.3
  5. E.56.5.
Show the answer and explanation

Answer: B (56.0)

Explanation

Total marks = 35 × 60 + 40 × 52.5 = 2100 + 2100 = 4200 for 75 students, so the mean is 4200 ÷ 75 = 56.0.

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Question 24

Data Presentation

A set of data contains a total of 130 items which are divided into six groups for display on a pie chart. If one group contains 26 items then the sector representing this group on the pie chart contains an angle x° at the centre of the circle where x is

  1. A.36
  2. B.60
  3. C.70
  4. D.72
  5. E.75.
Show the answer and explanation

Answer: D (72)

Explanation

The sector angle is 26/130 × 360° = 72°.

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Question 25

Triangles and Quadrilaterals

In triangle FGH, <G = 90°, <H = 60°, while in triangle XYZ, <X = 60° and <Y = 30°. From ΔXYZ write down the ratio equal to FG/FH

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

Answer: E (YZ/YX)

Explanation

<F = 30° and <Z = 90°, so F matches Y, G matches Z and H matches X. FG corresponds to YZ and FH to YX, so FG/FH = YZ/YX.

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Question 26

Angles and Polygons

A pentagon has four of its angles equal. If the size of the fifth angle is 60°, find the size of each of the four equal angles.

  1. A.60°
  2. B.108°
  3. C.120°
  4. D.150°
  5. E.None of the above.
Show the answer and explanation

Answer: C (120°)

Explanation

The angles of a pentagon add up to (5 − 2) × 180° = 540°. 540° − 60° = 480°, shared by four angles: 120° each.

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Question 28

Mensuration of Plane Shapes

In the figure above, FGHJ is a circle of radius 3cm centre O. FOH, GOJ are perpendicular diameters. With G as centre, an arc of a circle is drawn to pass through F and H. Find the length of the perimeter of the lunar portion shaded.

Diagram for this question
  1. A.3π(√2 − 1)cm
  2. B.3π(1 + √2/2) cm
  3. C.3π(1 + √2)cm
  4. D.9/2πcm
  5. E.9πcm.
Show the answer and explanation

Answer: B (3π(1 + √2/2) cm)

Explanation

The outer edge is half the small circle: π × 3 = 3π. The inner edge is an arc of radius GF = 3√2 subtending 90° at G: ¼ × 2π × 3√2 = 3√2π/2. Total 3π(1 + √2/2)cm.

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Question 29

Surds

Find the product of (2√y − 3y) and (3y + 2√y)

  1. A.4y + y2
  2. B.4y + 9y2
  3. C.4y − 9y2
  4. D.−4y − 9y2
  5. E.2y + y2.
Show the answer and explanation

Answer: C (4y − 9y2)

Explanation

This is (2√y − 3y)(2√y + 3y), a difference of two squares: (2√y)² − (3y)² = 4y − 9y².

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Question 31

Quadratic Equations

What will be the value of k so that the quadratic equation kx2 − 4x + 1 = 0 has two equal roots?

  1. A.2
  2. B.3
  3. C.4
  4. D.8
  5. E.¼
Show the answer and explanation

Answer: C (4)

Explanation

Equal roots need b² = 4ac: 16 = 4k, so k = 4.

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Question 33

Indices

If it is given that 5x + 1 + 5x = 150 then the value of x is equal to

  1. A.3
  2. B.4
  3. C.1
  4. D.2
  5. E.½.
Show the answer and explanation

Answer: D (2)

Explanation

5ˣ⁺¹ + 5ˣ = 5 × 5ˣ + 5ˣ = 6 × 5ˣ = 150, so 5ˣ = 25 = 5² and x = 2.

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Question 34

Linear and Simultaneous Equations

Solve the system of equation
2x + y = 32
33y − x = 27

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

Answer: A ((3, 2))

Explanation

32 = 2⁵ and 27 = 3³, so x + y = 5 and 3y − x = 3. Adding: 4y = 8, y = 2 and x = 3.

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Question 36

Mensuration of Solids

Find the area of the curved surface of a cone whose base radius is 6cm and whose height is 8cm. (Take π = 22/7)

  1. A.188.57cm2
  2. B.1320cm2
  3. C.188cm2
  4. D.188.08cm2
  5. E.100cm2
Show the answer and explanation

Answer: A (188.57cm2)

Explanation

The slant height is √(6² + 8²) = 10cm. Curved surface = πrl = 22/7 × 6 × 10 ≈ 188.57cm².

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Question 37

Trigonometry

Solve the equation for all positive values of θ less than 360°, 3 tan θ + 2 = −1

  1. A.135° or 315°
  2. B.45 or 135°
  3. C.315 or 45
  4. D.315 or 180
  5. E.360 or 315.
Show the answer and explanation

Answer: A (135° or 315°)

Explanation

3 tan θ = −3, so tan θ = −1. Tangent is negative in the 2nd and 4th quadrants: θ = 180° − 45° = 135° or 360° − 45° = 315°.

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Question 38

Logarithms

Given log 2 = 0.69, log 3 = 1.10 and log 7 = 1.90 all to a fixed base, find log 10.5 to the same base, without using tables.

  1. A.1.03
  2. B.2.31
  3. C.3.69
  4. D.10.5
  5. E.1.69.
Show the answer and explanation

Answer: B (2.31)

Explanation

10.5 = 3 × 7 ÷ 2, so log 10.5 = 1.10 + 1.90 − 0.69 = 2.31.

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Question 39

Logarithms

Simplify 102 + log105

  1. A.500
  2. B.2log105
  3. C.10
  4. D.25
  5. E.log107.
Show the answer and explanation

Answer: A (500)

Explanation

10^(2 + log₁₀5) = 10² × 10^(log₁₀5) = 100 × 5 = 500.

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Question 40

Algebraic Expressions

Simplify, as much as possible 1 + 2/(1 − 5/(5 + 2/x))

  1. A.2/x + 2
  2. B.x + 1
  3. C.10x + 6
  4. D.5x + 3
  5. E.(5x + 3)/(5x + 2)
Show the answer and explanation

Answer: D (5x + 3)

Explanation

5 + 2/x = (5x + 2)/x, so 5 divided by it is 5x/(5x + 2). Then 1 − 5x/(5x + 2) = 2/(5x + 2), and 2 divided by that is 5x + 2. Adding 1 gives 5x + 3.

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Question 41

Algebraic Expressions

Find the missing numerator: 5/(x + 1) − 3/(1 − x) − (7x − 1)/(x2 − 1) = ______/(x + 1)

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

Answer: E (1.)

Explanation

−3/(1 − x) = 3/(x − 1). Over x² − 1 the top is 5(x − 1) + 3(x + 1) − (7x − 1) = x − 1, so the whole is (x − 1)/(x² − 1) = 1/(x + 1).

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Question 42

Polynomials

The expression x3 − 4x2 + cx + d is such that x + 1 is its factor, and its value is 1 when x is −2. Find c and d.

  1. A.c = 4 and d = −9
  2. B.c = −4 and d = 9
  3. C.c = −20 and d = −15
  4. D.c = 20 and d = −15
  5. E.c = −20 and d = 15.
Show the answer and explanation

Answer: C (c = −20 and d = −15)

Explanation

f(−1) = −1 − 4 − c + d = 0 gives d − c = 5. f(−2) = −8 − 16 − 2c + d = 1 gives d − 2c = 25. Subtracting: c = −20, so d = −15.

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Question 43

Algebraic Expressions

If a function is defined by f(x + 1) = 3x2 − x + 4 find f(0)

  1. A.4
  2. B.6
  3. C.0
  4. D.8
  5. E.2.
Show the answer and explanation

Answer: D (8)

Explanation

f(0) means x + 1 = 0, i.e. x = −1: 3(1) + 1 + 4 = 8.

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Question 45

Triangles and Quadrilaterals

The angles marked in the figure above are measured in degrees. Find x

Diagram for this question
  1. A.45°
  2. B.90°
  3. C.60°
  4. D.15°
  5. E.30°.
Show the answer and explanation

Answer: E (30°.)

Explanation

The marked angles are the exterior angles of the pentagon, which add up to 360°: x + 2x + x + 5x + 3x = 12x = 360°, so x = 30°.

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Question 46

Circle Theorems

In the figure above, PS = SR and RX is a tangent to the circle at R, <QRX is equal to 72°. Find <SPR

Diagram for this question
  1. A.20°
  2. B.36°
  3. C.72°
  4. D.30°
  5. E.15°.
Show the answer and explanation

Answer: B (36°)

Explanation

By the alternate segment theorem <RSQ = <QRX = 72°. This is the exterior angle of isosceles triangle PSR, so 2 × <SPR = 72° and <SPR = 36°.

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Question 48

Variation

If x varies inversely as y, and y varies directly as the square root of z, and z varies directly as 1/w2, write down in words how x varies with w.

  1. A.x varies inversely as w2
  2. B.x varies directly as w2
  3. C.x varies directly as w
  4. D.x varies inversely as w
  5. E.x varies directly as square root of w.
Show the answer and explanation

Answer: C (x varies directly as w)

Explanation

√z ∝ 1/w, so y ∝ 1/w. Since x ∝ 1/y, x ∝ w.

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Question 49

Number Bases

Write the decimal number 39 to base 2

  1. A.100111
  2. B.110111
  3. C.111001
  4. D.100101
  5. E.19.5.
Show the answer and explanation

Answer: A (100111)

Explanation

39 = 32 + 4 + 2 + 1, so in base 2 it is 100111.

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Question 50

Mensuration of Plane Shapes

Find the area of the shaded segment in the figure shown above

Diagram for this question
  1. A.√3
  2. B.4π − √3
  3. C.2/3π
  4. D.2π/3 − √3
  5. E.2π/3 − 2√3
Show the answer and explanation

Answer: D (2π/3 − √3)

Explanation

Sector = 60/360 × π × 2² = 2π/3. Triangle = ½ × 2 × 2 × sin 60° = √3. Segment = 2π/3 − √3.

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