WAEC Past Questions and Answers - Page 4186

20,926.

The curved surface area of a cylindrical tin is 704cm\(^2\). Calculate the height when the radius is 8cm. [Take π = 22/7]

A.

3.5cm

B.

7cm

C.

14cm

D.

28cm

E.

32cm

Correct answer is C

Curved surface area of a cylindrical tin = \(2\pi rh\)

\(\therefore 2\pi rh = 704cm^2\)

\(2 \times \frac{22}{7} \times 8 \times h = 704\)

\(h = \frac{704 \times 7}{2 \times 22 \times 8}\)

\(h = 14cm\)

20,927.

The angle of a sector of a circle of radius 8cm is 240°. This sector is bent to form a cone. Find the radius of the base of the cone.

A.

16/3cm

B.

15/3cm

C.

16/5cm

D.

8/3cm

E.

16/10cm

Correct answer is A

L = θ/360 x 2πR = 240/360 x 2 x 22/7 x 8/1 ... (1)

This must be equal to the circumference of the circle which is 2πr = 44R/7 .... (2)

equate (1) and (2)

r = 16/3 = 51/3

20,928.

Solve the equation \(\frac{m}{3} + \frac{1}{2} = \frac{3}{4} + \frac{m}{4}\)

A.

-3

B.

-2

C.

2

D.

3

E.

4

Correct answer is D

\(\frac{m}{3} + \frac{1}{2} = \frac{3}{4} + \frac{m}{4}\)

\(\frac{m}{3} - \frac{m}{4} = \frac{3}{4} - \frac{1}{2}\)

\(\frac{m}{12} = \frac{1}{4}\)

\(4m = 12 \implies m = 3\)

20,929.

What must be added to the expression x\(^2\) - 18x to make it a perfect square?

A.

3

B.

9

C.

36

D.

72

E.

81

Correct answer is E

x\(^2\) - 18x to be a perfect square.

\((\frac{b}{2})^2\) is added to ax\(^2\) + bx + c in order to make it a perfect square.

\(x^2 - 18x + (\frac{-18}{2})^2\)

= \(x^2 - 18x + 81\)

20,930.

Write as a single fraction \(\frac{1}{1 - x} + \frac{2}{1 + x}\)

A.

\(\frac{x + 3}{1 - x^2}\)

B.

\(\frac{3 - x}{(1 - x)^2}\)

C.

\(\frac{3 - x}{1 + x^2}\)

D.

\(\frac{3 - x}{(1 + x)^2}\)

E.

\(\frac{3 - x}{1 - x^2}\)

Correct answer is E

\(\frac{1}{1 - x} + \frac{2}{1 + x}\)

= \(\frac{(1 + x) + 2(1 - x)}{(1 - x)(1 + x)}\)

= \(\frac{1 + x + 2 - 2x}{1 - x^2}\)

= \(\frac{3 - x}{1 - x^2}\)