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WAEC Mathematics Past Questions & Answers - Page 118

586.

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

View answer & explanation

Correct answer is A

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

38 = 19 = n(C) - 7

n(C) = 38 - 12

= 26

587.

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

225

View answer & explanation

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

588.

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

$\frac{3}{4}$

$\frac{1}{2}$

$\frac{1}{4}$

View answer & explanation

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 = $\frac{1}{2}$

589.

Simplify $\frac{m}{n} + \frac{(m - 1)}{5n} = \frac{(m - 2)}{10n}$ where n $\neq$ 0

$\frac{m - 3}{10n}$

$\frac{11m}{10n}$

$\frac{m + 1}{10n}$

$\frac{11m + 4}{10n}$

View answer & explanation

Correct answer is B

$\frac{m}{n} + \frac{(m - 1)}{5n} - \frac{(m - 2)}{10n}$ ; $\frac{10m + 2(m - 1) - 1(m - 2)}{10m}$

= $\frac{10m + 2m - 2 - m + 2}{10n}$

= $\frac{10m + 2m - m - 2 + 2}{10n}$

= $\frac{11m}{10n}$

590.

The graph represents the relation y = x^o2 - 3x - 3. Find the value of x for which x² - 3x = 7

-1.55, 4.44

1.55, -4.55

-1.55, -4.55

1.55, 4.55

View answer & explanation

Correct answer is A

x² - 3x = 7

x² - 3x - 7 = 0

What can you add to both sides of the equation to give the same value of y = x² - 3x - 3

The number is 4

x² - 3x - 7 + 4 = 4

x² - 3x - 3 = 4

but y = x² - 3x - 3

y = 4; So are y = 4 draw a line parallel to x axis, to cut or intersect the graph. At these points look down to see the corresponding values on x axis

This give -1.55 and 4.55