WAEC Mathematics Past Questions & Answers - Page 98

486.

The distance between two towns is 50km. It is represented on a map by 5cm. Find the scale used

A.

1: 1,000,000

B.

1: 500,000

C.

1: 100,000

D.

1: 10,000

Correct answer is A

1km = 100,000cm

on the map 1 cm represent every 10 km which is equal to (10 x 100,000cm)

= 1,000,000cm

the scale is 1:1,000,000

487.

The slant height of a cone is 5cm and the radius of its base is 3cm. Find, correct to the nearest whole number, the volume of the cone. ( Take \(\pi = \frac{22}{7}\))

A.

48cm3

B.

47cm3

C.

38cm3

D.

12cm3

Correct answer is C

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

h2 = 52 = 32

= 25 - 9 = 16

h = \(\sqrt{16}\)

h = 4cm

v = \(\frac{1}{3} \times \frac{22}{7} \times 3^2 \times 4\)

\(\frac{1}{3} \times \frac{22}{7} \times 9 \times 4\)

= \(\frac{22 \times 3 \times 4}{7}\)

= 37.7cm3

= 38cm3

488.

A pyramid has a rectangular base with dimensions 12m by 8m. If its height is 14m, calculate the volume

A.

322m3

B.

448m3

C.

632m2

D.

840m2

Correct answer is B

Volume of pyramid = \(\frac{1}{3}\) x base area x height

= \(\frac{1}{3} \times 12^4 \times 8 \times 14\)

= 4 x 8 x 14 = 448m3

489.

Given that P = x2 + 4x - 2, Q = 2x - 1 and Q - p = 2, find x

A.

-2

B.

-1

C.

1

D.

2

Correct answer is B

P = x2 + 4x - 2, Q = 2x - 1

Q - p = 2, (2x - 1) - (x2 + 4x - 2) = 2

2x - 1 - x2 - 4x + 2 = 2

-2x - x2 + 1

-x2 - 2x - 1 = 0

x2 + 2x + 1 = 0

x2 + x + x + 1 = 0

x(x + 1) + 1(x + 1) = 0

(x + 1)(x + 1) = 0

x + 1 = 0 or x + 1 = 0

x = -1 or x = -1

x = -1

490.

An interior angle of a regular polygon is 5 times each exterior angle. How many sides has the polygon?

A.

15

B.

12

C.

9

D.

6

Correct answer is B

Let the interior angle = xo

interior angle = 5xo (sum of int. angle ann exterior)

(angles = angle or straight line)

6x = 180

x = \(\frac{180}{6}\)

x = 30o

no. of sides = \(\frac{\text{sum of exterior angles}}{\text{exterior angle}}\)

= \(\frac{360}{30}\) = 12