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WAEC Mathematics Past Questions & Answers - Page 16

76.

Find the area of the sector OPSQ

A.

15.40cm2

B.

17.64cm2

C.

23.10cm2

D.

32.34cm2

Correct answer is D

\frac{θ}{360}  *π * r^2 → \frac{210 * 22 * 4.2 * 4.2}{360 * 7}

\frac{1617}{50} = 32.34cm^2

77.

In the diagram, ∠POQ = 150 and the radius of the circle PSQR is 4.2cm. [take π = 22/7]

What is the length of the minor arc?

A.

11cm

B.

15.4cm

C.

17.64cm

D.

23.10cm

Correct answer is A

\frac{θ}{360}  * 2 * π * r → \frac{150 * 2 * 22 * 4.2}{360 x 7}

= 11cm

78.

An exterior angle of a regular polygon is 22.5°. Find the number of sides.

A.

13

B.

14

C.

15

D.

16

Correct answer is D

The sum of exterior angles of a polygon is 360°

\frac{360}{22.5} = 16 sides

79.

Make t the subject of k = m \sqrt \frac{t-p}{r}

A.

\frac{k^2r + p}{m^2}

B.

\frac{k^2r + pm^2}{m^2}

C.

\frac{k^2r - p}{m^2}

D.

\frac{k^2r + p^2}{m^2}

Correct answer is B

square both sides to remove the square root

k^2 = m^2 \frac{t-p}{r}

\frac{k^2r}{m^2} = t - p

t = \frac{k^2r}{m^2} + p

t = \frac{k^2r + pm^2}{m^2} 

80.

Find the value of x such that \frac{1}{x} +\frac{4}{3x}\frac{5}{6x} + 1 = 0

A.

\frac{1}{6}

B.

\frac{1}{4}

C.

\frac{-3}{2}

D.

\frac{-7}{6}

Correct answer is C

\frac{1}{x} +\frac{4}{3x}\frac{5}{6x} + 1 = 0
using 6x as lcm

→ \frac{6+8-5+6x}{6x} 

→ \frac{9+6x}{6x} = 0

9+6x = 0

6x = -9

x = \frac{-9}{6}  or \frac{-3}{2}