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WAEC Mathematics Past Questions & Answers - Page 168

836.

Simplify: 11011 $_2$ - 1101 $_2$

101000 $_2$

1100 $_2$

1110 $_2$

1011 $_2$

View answer & explanation

Correct answer is C

11011 $_2$ - 1101 $_2$ = 1110 $_2$

837.

Evaluate (0.13) $^3$ correct to three significant figures

0.00219

0.00220

0.00300

0.00390

View answer & explanation

Correct answer is B

(0.13) $^3$ = 0.13 x 0.13 x 0.13 = 0.002197

= 0.00220 (3 s.f)

838.

P varies directly as Q and inversely as R. When Q = 36 and R = 16, P = 27. Find the relation between P, Q and R.

$P = \frac{Q}{12R}$

$P = \frac{12Q}{R}$

$P = 12QR$

$P = \frac{12}{QR}$

View answer & explanation

Correct answer is B

$P \propto \frac{Q}{R}$

$P = K \frac{Q}{R}$

When Q = 36, R = 16, P = 27

Then substitute into the equation

$27 = K \frac{36}{16}$

$K = \frac{27 \times 16}{36}$

$K = 12$

So the equation connecting P, Q and R is

$P = \frac{12Q}{R}$

839.

y varies directly as w². When y = 8, w = 2. Find y when w = 3

View answer & explanation

Correct answer is A

$y \propto w^2$

y = kw²

8 = k(2)²

8 = k(4)

k = 8/4

k = 2

Thus y = 2w²
When w = 3, y = 2(3)²

y = 2 x 9 = 18

840.

Find the value of k if y - 1 is a factor of y³ + 4y² + ky - 6

-6

-4

View answer & explanation

Correct answer is D

if y - 1 is a factor of y³ + 4y² + ky - 6, then

f(1) = (1)³ + 4(1)2 + k(1) - 6 = 0 (factor theorem)

1 + 4 + k - 6 = 0

5 - 6 + k = 0

-1 + k = 0

k = 1