WAEC Mathematics Past Questions & Answers - Page 41

201.

In the diagram, POS and ROT are straight lines. OPQR is a parallelogram, |OS| = |OT| and OST = 50°. Calculate the value of OPQ.

A.

100\(^o\)

B.

120\(^o\)

C.

140\(^o\)

D.

160\(^o\)

Correct answer is A

S\(O\)T = 180\(^o\) - (50 + 50) 

= 80\(^o\) 

P\(Q\)R = 80\(^o\)

= \(\frac{360^o - 160^o}{2}\) = 100\(^o\)

202.

A rectangular board has a length of 15cm and width x cm. If its sides are doubled, find its new area.

A.

60x cm\(^2\)

B.

45x cm\(^2\)

C.

30x cm\(^2\)

D.

15x cm\(^2\)

Correct answer is A

New are = (2 x 15) x (2 x \(x\)) 

= 60cm\(^2\)

203.

Find the angle at which an arc of length 22 cm subtends at the centre of a circle of radius 15cm.  [Take \(\pi = \frac{22}{7}\)]

A.

70\(^o\)

B.

84\(^o\)

C.

96\(^o\)

D.

156\(^o\)

Correct answer is B

L = \(\frac{\theta}{360} \times 2 \pi r\)

22 = \(\frac{theta}{360} \times 2 \times \frac{22}{7} \times 15\)

\(\theta = \frac{22 \times 360 \times 7}{2 \times 22 \times 15}\)

\(\theta\) = 84\(^o\) 

204.

Eric sold his house through an agent who charged 8% commission on the selling price. If Eric received $117,760.00 after the sale, what was the selling price of the house? 

A.

$130,000.00

B.

$128,000.00

C.

$125,000.00

D.

$120,000.00

Correct answer is B

\(\frac{8}{100} \times x + 117,760 = x\)

x - \(\frac{8x}{100} = 117,760

\(\frac{92x}{100} = 117,760\)

x = \(\frac{117,760 \times 100}{92}\)

Selling price = N128,000

205.

Make b the subject of the relation lb = \(\frac{1}{2}\) (a + b)h

A.

\(\frac{ah}{2l - h}\)

B.

\(\frac{2l - h}{al}\)

C.

\(\frac{al}{2l - h}\)

D.

\(\frac{al}{2 - h}\)

Correct answer is A

lb = \(\frac{1}{2} (a + b)h

2lb = ah + bh

2lb - bh = ah

\(\frac{b(2l - h)}{2l - h} = \frac{ah}{2l - h}\)

b = \(\frac{ah}{2l - h}\)