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WAEC Mathematics Past Questions & Answers - Page 163

811.

The values of three angles at a point are 3y - 45^o, y + 25^o and y^o . Find the value of y.

40^o

58^o

68^o

76^o

View answer & explanation

Correct answer is D

(3y - 450 + (y + 25) + t = 360^o(angles at a point)

3y - 45 + y + 25 + y = 360

5y = 360 + 20

5y = 380

y = $\frac{380}{5}$

= 76^o

812.

If p = {1, 3, 5, 7, 9} and Q = {2, 4, 6, 8, 10} are subsets of a universal set. U = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}. What are the elements of P¹ $\cap$ Q¹?

{1, 3, 5, 7, 9}

[2, 4, 6, 8, 10}

$\varnothing$

{1, 2, 6, 8, 10}

View answer & explanation

Correct answer is C

P¹ = {2, 4, 6, 8, 10}; {1, 3, 5, 7, 9}

P¹ $\cap$ q¹ = {} or $\varnothing$

813.

The wheel of a tractor has a diameter 1.4m. What distance does it cover in 100 complete revolutions? [Take $\pi = \frac{22}{7}$ ]

140m

220m

280m

440m

View answer & explanation

Correct answer is D

radius = $\frac{diameter}{2}$ = $\frac{1.4}{2}$

= 0.7m

circumference = 2 $\pi r = 2 \times \frac{22}{7} \times 0.7m = 4.4m$

distance covered = 4.4m x 100 = 440m

814.

A seller allows 20% discount for cash payment on the marked price of his goods. What is the ratio of the cash payment to the marked price

1:4

1:5

3:4

4:5

View answer & explanation

Correct answer is D

(1 - $\frac{20}{100}$ ) = cash payment fraction= $\frac{4}{5}$

The ratio of the cash payment to the marked price = 4:5

815.

If p = [ $\frac{Q(R - T)}{15}$ ] $^ \frac{1}{3}$ , make T the subject of the relation

T = R + $\frac{P^3}{15Q}$

T = R - $\frac{15P^3}{Q}$

T = R + $\frac{P^3}{15Q}$

T = 15R - $\frac{Q}{P^3}$

View answer & explanation

Correct answer is B

Cubic both sides; P³ = $\frac{Q(R - T)}{15}$

(cross multiplication) Q(R - T) = 15P³

(divide both sides by Q); R - T = 15 $\frac{1}{Q}$

(subtract r from both sides) - T = $\frac{15P^3}{Q - R}$

T = R - $\frac{15P^3}{Q}$