WAEC Mathematics Past Questions & Answers - Page 153

761.

The volume of a cylinder is 1200cm3 and the area of its base is 150cm2. Find the height of the cylinder.

A.

80.00cm

B.

8.00cm

C.

0.80cm

D.

0.08cm

Correct answer is B

Vol. of cylinder = \(\pi r^2h\) = 1200cm2

Area of base = \(\pi^2\) = 150cm2

h = \(\frac{\pi r^2}{\pi r^2} = \frac{1200}{150}\)

= 8.00cm

762.

Two circles have radii 16cm and 23cm. What is the difference between their circumference? take \(\pi = \frac{22}{7}\)

A.

422.92cm

B.

149.92cm

C.

44.00cm

D.

43.96cm

Correct answer is C

r = 16, R = 23; 2\(\pi R - 2 \pi r\)

= 2\(\pi(R - r)\)

= 2 x \(\frac{22}{7} (23 - 16)\)

= 2 x \(\frac{22}{7} \times (7)\)

= 44cm

763.

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

A.

-1

B.

-2x

C.

2x

D.

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

Correct answer is A

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

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

= 1

764.

Expand the expression(3a - xy)(3a + xy)

A.

9a2 - x2y2

B.

9a2 + x2y2

C.

9a2 - xy

D.

9a2 + x2y

Correct answer is A

(3a - xy)(3a + xy); (3a)2 - (xy)2

difference of two sqs; 9a2 - x2y2

765.

Find the smallest value of k such that 2\(^2\) x 3\(^3\) x 5 x k is a perfect square.

A.

3

B.

5

C.

15

D.

30

Correct answer is C

2\(^2\) x 3\(^3\) x 5\(^1\) x k;

2\(^2\) x 3\(^2\) x 3 x 5 x k

2\(^2\) x 3\(^2\) x 15 x k

smallest value for k

2\(^2\) x 3\(^2\) x 15 = 2\(^2\) x 3\(^2\) x 15\(^2\)

k = 15