Processing math: 17%

WAEC Mathematics Past Questions & Answers - Page 10

46.

The angle of a sector of a circle of radius 3.4 cm is 115°. Find the area of the sector.

$(Take \pi = \frac{22}{7})$

$11.6cm^2$

$12.7cm^2$

$10.2cm^2$

$9.4cm^2$

View answer & explanation

Correct answer is A

$\theta = 115° , radius = 3.4cm^2$

Area of a sector = $\frac{\theta}{360} \times \pi r^2$

= $\frac{115}{360} \times \frac{22}{7} \times 3.4\times 3.4$

= $\frac{29246.4}{2520}$

= $11.6cm^2$

47.

The population of a village decreased from 1,230 to 1,040 due to breakout of an epidemic. What is the percentage decrease in the population?

15.44%

15.43%

15.42%

15.45%

View answer & explanation

Correct answer is D

Original population = 1,230
New population = 1,040
Decrease in population = 1,230 – 1,040 = 190
Percentage decrease in population = decrease in population x 100%
original population

= $\frac {190}{1,230}$ x 100 = 15.45%

48.

Let '*' and '^' be two binary operations such that a * b = a $^2$ b and a ^ b = 2a + b. Find (-4 * 2) ^ (7 * -1).

-49

113

View answer & explanation

Correct answer is D

Given that, a * b = a $^2$ b and a ^ b = 2a + b

(-4 * 2) = (-4) $^2$ x 2 = 16 x 2 = 32

(7 * -1) = 7 $^2$ x (-1) = 49 x (-1) = -49

∴ (-4 * 2) ^ (7 * -1) = 2(32) + (-49) = 64 - 49 = 15