WAEC Mathematics Past Questions & Answers - Page 169

841.

Simplify: 11011\(_2\) - 1101\(_2\)

A.

101000\(_2\)

B.

1100\(_2\)

C.

1110\(_2\)

D.

1011\(_2\)

Correct answer is C

11011\(_2\) - 1101\(_2\) = 1110\(_2\)

842.

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

A.

0.00219

B.

0.00220

C.

0.00300

D.

0.00390

Correct answer is B

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

= 0.00220 (3 s.f)

843.

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.

A.

\(P = \frac{Q}{12R}\)

B.

\(P = \frac{12Q}{R}\)

C.

\(P = 12QR\)

D.

\(P = \frac{12}{QR}\)

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

\(P = \frac{12Q}{R}\)

844.

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

A.

18

B.

12

C.

9

D.

6

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

845.

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

A.

-6

B.

-4

C.

0

D.

1

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