WAEC Mathematics Past Questions & Answers - Page 303

1,511.

The area of a parallelogram is 513cm\(^2\) and the height is 19cm. Calculate the base.

A.

13.5cm

B.

25cm

C.

27cm

D.

54cm

E.

108cm

Correct answer is C

Area of parallelogram = base \(\times\) height.

\(513 = base \times 19 \implies base = \frac{513}{19}\)

= 27 cm

1,512.

The volume of a cone of height 9cm is 1848cm\(^3\). Find its radius. [Take π = 22/7]

A.

7cm

B.

14cm

C.

28cm

D.

98cm

E.

196cm

Correct answer is B

1/3 πr\(^2\) x 9 = 1848
3 x πr2 = 1848 r2 = 1848/3 x 7/22 r = 14

\(\text{Volume of a cone} = \frac{1}{3} \pi r^2 h\)

\(\frac{1}{3} \times \frac{22}{7} \times r^2 \times 9 = 1848\)

\(r^2 = \frac{1848 \times 7}{22 \times 3}\)

\(r^2 = 196 \therefore r = 14cm\)

1,513.

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 = \(2\pi rh\)

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

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

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

\(h = 14cm\)

1,514.

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

1,515.

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

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

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

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

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