WAEC Mathematics Past Questions & Answers - Page 164

816.

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

A.

40o

B.

58o

C.

68o

D.

76o

Correct answer is D

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

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

5y = 360 + 20

5y = 380

y = \(\frac{380}{5}\)

= 76o

817.

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?

A.

{1, 3, 5, 7, 9}

B.

[2, 4, 6, 8, 10}

C.

\(\varnothing\)

D.

{1, 2, 6, 8, 10}

Correct answer is C

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

P1 \(\cap\) q1 = {} or \(\varnothing\)

818.

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

A.

140m

B.

220m

C.

280m

D.

440m

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

819.

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

A.

1:4

B.

1:5

C.

3:4

D.

4:5

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

820.

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

A.

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

B.

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

C.

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

D.

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

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 - \(\frac{15P^3}{Q}\)