WAEC Mathematics Past Questions & Answers - Page 16

76.

A ladder 6m long leans against a vertical wall at an angle 53º to the horizontal. How high up the wall does the ladder reach?

A.

3.611m

B.

4.521m

C.

4.792m

D.

3.962m

Correct answer is C

Sin θ = \(\frac{opp}{hyp}\) → \(\frac{x}{6}\)

cross multiply:

sin53º * 6 = x

0.7986 * 6

 4.792m

77.

Find the area of the sector OPSQ

A.

15.40cm\(^2\)

B.

17.64cm\(^2\)

C.

23.10cm\(^2\)

D.

32.34cm\(^2\)

Correct answer is D

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

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

78.

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

79.

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

80.

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 = \(\frac{k^2r + pm^2}{m^2}\)