WAEC Mathematics Past Questions & Answers - Page 118

586.

Simplify 1\(\frac{3}{4} - (2 \frac{1}{3} + 4)\)

A.

3\(\frac{5}{12}\)

B.

2\(\frac{7}{12}\)

C.

-4 \(\frac{7}{12}\)

D.

-5 \(\frac{7}{12}\)

Correct answer is C

1\(\frac{3}{4} - (2 \frac{1}{3} + 4)\) = \(\frac{7}{4} - (\frac{7}{3} + \frac{4}{1})\); \(\frac{7 + 12}{3}\)

\(\frac{7}{4} - \frac{19}{3} = \frac{21 + 76}{12}\)


= \(\frac{-55}{12} = -4 \frac{7}{12}\)

587.

What must be added to (2x - 3y) to get (x - 2y)?

A.

5y - x

B.

y - x

C.

x - 5x

D.

x - y

Correct answer is B

What must be added to 2x - 3y = Difference between x - 2y and 2x - 3y

x - 2y - 2y - (2x - 3y); x - 2y - 2x + 3y

= x - 2x + 3y - 2y

= y - x

588.

Given that n(p) = 19, m(P \(\cup\) Q) = 38 and n(P \(\cap\) Q) = 7, Find n(C)

A.

26

B.

31

C.

36

D.

50

Correct answer is A

n(P \(\cup\) Q) = m(P \(\cap\) C)

38 = 19 = n(C) - 7

n(C) = 38 - 12

= 26

589.

G varies directly as the square of H, If G is 4 when H is 3, find H when G = 100

A.

15

B.

25

C.

75

D.

225

Correct answer is A

G \(\alpha\) H2

G = KH2

4 = K(3)2

4 = 9k; K = \(\frac{4}{9}\)

100 = \(\frac{4}{9}H^2\)

4H2 = 900

H2 = \(\frac{900}{4}\)

H2 = 225

H = \(\sqrt{225}\)

H = 15

590.

If \(\sqrt{72} + \sqrt{32} - 3 \sqrt{18} = x \sqrt{8}\), Find the value of x

A.

1

B.

\(\frac{3}{4}\)

C.

\(\frac{1}{2}\)

D.

\(\frac{1}{4}\)

Correct answer is C

\(\sqrt{2} + \sqrt{32} - 3\sqrt{18} = x\sqrt{8}\)

= \(\sqrt{36 \times 2} + \sqrt{16 \times 2} - 3\sqrt{2 \times 9}\)

= x\(\sqrt{2 \times 4}\)

= 6\(\sqrt{2} + 4\sqrt{2} - 9\sqrt{2} = 2 \times \sqrt{2}\)

\(\sqrt{2} (6 + 4 - 9) = 2x\sqrt{2}\)

\(\sqrt{2} = 2x \sqrt{2}\) divide both sides by \(\sqrt{2}\)

\(\frac{\sqrt{2}}{\sqrt{2}} = \frac{2 \times \sqrt{2}}{\sqrt{2}}\)

1 = 2x

2x = 1

x = \(\frac{1}{2}\)