WAEC Mathematics Past Questions & Answers - Page 43

211.

The total surface area of a solid cylinder 165cm\(^2\). Of the base diameter is 7cm, calculate its height. [Take \(\pi = \frac{22}{7}\)]

A.

7.5 cm

B.

4.5 cm

C.

4.0 cm

D.

2.0 cm

Correct answer is C

165 = 2 x \(\frac{22}{7}\) x \(\frac{7}{2}\) x h + 2 x \(\frac{22}{7}\) x \(\frac{7}{2}\) x \(\frac{7}{2}\)

165 = 22h + 77 

\(\frac{22h}{22} = \frac{88}{22}\)

height = 4cm

212.

Which of these values would make \(\frac{3p^-}{p^{2-}}\) undefined? 

A.

1

B.

\(\frac{1}{3}\)

C.

-\(\frac{1}{3}\)

D.

-1

Correct answer is A

P\(^2\) - p = 0

p(p - 1) = 0

p = 0 or p = 1

213.

Simplify: \(\frac{x^2 - 5x - 14}{x^2 - 9x + 14}\) 

A.

\(\frac{x - 7}{x + 7}\)

B.

\(\frac{x + 7}{x - 7}\)

C.

\(\frac{x - 2}{x + 4}\)

D.

\(\frac{x + 2}{x - 2}\)

Correct answer is D

\(\frac{x^2 - 5x - 14}{x^2 - 9x + 14}\)

\(\frac{(x - 7)(x + 2)}{(x - 7)(x - 2)}\)

= \(\frac{x + 2}{x - 2}\) 

214.

There are 8 boys and 4 girls in a lift. What is the probability that the first person who steps out of the lift will be a boy? 

A.

\(\frac{1}{6}\)

B.

\(\frac{1}{4}\)

C.

\(\frac{2}{3}\)

D.

\(\frac{1}{2}\)

Correct answer is C

Total number of people in the lift = 8 boys + 4 girls

= 12 people

probability that a boy comes out = \(\frac{8}{12}\) = \(\frac{2}{3}\) 

215.

If (0.25)\(^y\) = 32, find the value of y.

A.

y = - \(\frac{5}{2}\)

B.

y = -\(\frac{3}{2}\)

C.

y = \(\frac{3}{2}\)

D.

y = \(\frac{5}{2}\)

Correct answer is A

(0.25)\(^y\) = 32

2\(^{-2y}\) = 3\(^{2}\)

2 - 2y = 5 

y = - \(\frac{5}{2}\)