2008 - WAEC Mathematics Past Questions and Answers - page 1

x% of 240 = 12

\(\frac{x}{100} \times 240 = 12\)

x = \(\frac{12 \times 100}{240}\)

x = 5

\(\frac{(3.2)^2 - (4.8)^2}{3.2 + 1.8} = \frac{(3.2 - 4.8)(3.2 + 4.8)}{(3.2 + 4.8)}\)

= 3.2 - 4.8

= -1.60

\(\sqrt{50} + \frac{10}}{\sqrt{2}} = \(\frac{\sqrt{50}}{1} + \sqrt{10}{\sqrt{2}}\)

= \(\frac{\sqrt{50 \times 2} + 10}{\sqrt{2}}\)

= \(\frac{\sqrt{100} + 10}{\sqrt{2}}\)

= \(\frac{10 + 10}{\sqrt{2} = \frac{20}{\sqrt{2}}\)

= \(\frac{20}{\sqrt{2}}\) \times \frac{\sqrt{2}}{\sqrt{2}}\)

= \(\frac{20\sqrt{2}}{2}\)

= 10\(\sqrt{2}\)

I = \(\frac{PRT}{100}\)

where r = r% p.a; I = 0.36p

0.36p = \(\frac{P \times r \times 4}{100}\)

\(\frac{0.36 \times 100}{4}\) = r

r = 9

Cost price, c.p = \(\frac{100}{5}\) x N350 = N7000

Selling price, s.p = \(\frac{100}{5}\) x N290 = N7250

%Gain = \(\frac{S.p - C.p}{C.p}\) x 100%

= \(\frac{7250 - 7000}{7000}\) x 100% = \(\frac{250 \times 100}{7000}\)

= 3.6% (approx.)

p - 2g + 1 = g + 3p.........(1)

p - 2 = 0 .........(2)

From (2), p = 2; put p = 2 into (1);

2 - 2g + 1 = g + 3(2)

3 - 2g = g + 6

-2g - g = 6 - 3

-3g = 3

g = \(\frac{3}{-3}\)

g = -1

\(\frac{\frac{1}{x} + \frac{1}{y}}{x + y}\) = \(\frac{\frac{y + x}{xy}}{x + y}\)

= \(\frac{x + y}{xy}\)

= \(\frac{x + y}{xy} \times \frac{1}{x + y}\)

= \(\frac{1}{xy}\)

3\(\sqrt{27x^3y^9}\) = 3\(\sqrt{27} \times 3\sqrt{3^3} \times 3\sqrt{y^9}\)

= 3 \(\times x \times y^3\)

= 3xy³

Given; x = 2; y = \(\frac{-1}{4}\)

= \(\frac{x^2y - 2xy}{5}\)

= \(\frac{2^2(\frac{-1}{4}) - 2(2)(\frac{-1}{4})}{5}\)

= \(\frac{4(\frac{-1}{4}) + 4(\frac{-1}{4})}{5}\)

= \(\frac{1 + 1}{5}\)

= \(\frac{0}{5}\)

= 0

5y² + 2ay - 3a² = 5y² + 5ay - 3a²

= 5y(y + a) - 3a(y + a)

= (y + a)(5y - 3a)