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WAEC Mathematics Past Questions & Answers - Page 22

106.

In the diagram, line ¯EC is a diameter of the circle ABCDE.

If angle ABC equals 158°, find ∠ADE

A.

112

B.

90

C.

68

D.

22

Correct answer is C

No explanation has been provided for this answer.

107.

Given that sin x = 3/5, 0 ≤ x ≤ 90, evaluate (tanx + 2cosx)

A.

21120

B.

1120

C.

2720

D.

120

Correct answer is B

Sin x = opphyp

sinx = 35

using Pythagoras' theorem

 hyp2 = opp2 + adj2

adj2 = 52 - 32 = 25 - 9

adj2 = 16 

adj =  16 

adj = 4.

tanx = oppadj

34

cosx = adjhyp

45

(tanx + 2cosx) = 34 + 2(45)

15+3220

4720 or 

2 720

108.

A cone has a base radius of 8cm and height 11cm. calculate , correct to 2d.p, the curved surface area

A.

341.98cm2

B.

276.57cm2

C.

201.14cm2

D.

477.71cm2

Correct answer is A

Where l2 = h2 + r2

l2 = 112 + 82

l = √185

l = 13.60cm

The formula of CSA of Cone is πrl

227 * 8 * 13.60

= 341.979 or 341.98 (2d.p)

109.

In the diagram, PQRS is a circle. find the value of x.

A.

50°

B.

30°

C.

80°

D.

100°

Correct answer is A

Opp. angles in a cyclic quadrilateral always add up to 180°

∠P + ∠R & ∠Q + ∠S = 180

x + x+y = 180 

2x + y = 180... i

2y - 30 + x = 180 

2y + x = 180 + 30

x + 2y = 210 ... ii

Elimination method:

(2x + y = 180) * 1 --> 2x + y = 180

(x + 2y = 210) * 2 --> 2x + 4y = 420

Subtracting both equations

- 3y = - 240

y = 80°

using eqn i

2x + y = 180

2x + 80 = 180

2x = 100

x = 50°

110.

find the first quartile of 7,8,7,9,11,8,7,9,6 and 8.

A.

8.5

B.

7.0

C.

7.5

D.

8.0

Correct answer is B

Rearrange data in increasing order: 6,7,7,7,8,8,8,9,9 and 11

First quartile (ungrouped data) = n4th value

104 

= 2.5th value

7+72

= 7.0