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WAEC Mathematics Past Questions & Answers - Page 67

331.

The relation y = x² + 2x + k passes through the point (2,0). Find the value of k

- 8

- 4

View answer & explanation

Correct answer is A

Y = x² + 2x + k (given)

y = o when x = 2

thus 0 = 2² + 2 x 2 + k

0 = 4 + 4 + k

given k = -8

332.

A bag contains 5 red and 4 blue identical balls. Id two balls are selected at random from the bag, one after the other, with replacement, find the probability that the first is red and the second is blue

$\frac{2}{9}$

$\frac{5}{18}$

$\frac{20}{81}$

$\frac{5}{9}$

View answer & explanation

Correct answer is C

n(red balls) = 5

n(blue balls) = 4

n( $\iff$ ) = 9

Hence, prob (R₁, B₂)

= $\frac{5}{9} \times \frac{4}{9}$

= $\frac{20}{81}$

333.

In the diagram, O is the centre of the circle, < QPS = 100^o, < PSQ = 60^o and < QSR. Calculate < SQR

20^o

40^o

60^o

80^o

View answer & explanation

Correct answer is A

In the diagram, < RPQ = 80^o(angles in same segment)

< SPR = 100^o - < RPQ

= 100 - 80

= 20^o

< SQR = < SPR = 20^o (same reason as above)

< SQR = 20^o

334.

Simplify $\frac{(p - r)^2 - r^2}{2p^2 - 4pr}$

$\frac{1}{2}$

p - 2r

$\frac{1}{p - 2r}$

$\frac{2p}{p - 2r}$

View answer & explanation

Correct answer is A

$\frac{(p - r)^2 - r^2}{2p^2 - 4pr}$

= $\frac{(p - r)(p - r) - r^2}{2p^2 - 4pr}$ \

= $\frac{p^2 - 2pr + r^2 - r^2}{2p(p - 2r}$

= $\frac{p^2 - 2pr}{2p(p - 2r)}$

= $\frac{p(p - 2r)}{2p(p - 2r)}$

= $\frac{1}{2}$