WAEC Mathematics Past Questions & Answers - Page 103

% error = $\frac{error}{\text{actual value}} \times 100$

error = N72 - N68 = 4

actual value = N72

%error = $\frac{4}{72} \times 100$

= $\frac{100}{18} = \frac{50}{9}$ = 5$\frac{5}{9}$%

$\sqrt{50} - K\sqrt{8} = \frac{2}{\sqrt{2}}$

$\sqrt{50} - \frac{2}{\sqrt{2}}$ = K$\sqrt{8}$

= $\sqrt{2} \times 25 - \frac{2}{\sqrt{2}}$

= K $\sqrt{4 \times 2}$

$\frac{5\sqrt{2}}{1} - \frac{2}{\sqrt{2}}$ = 2K$\sqrt{2}$

$\frac{5\sqrt{4} - 2}{\sqrt{2}} = 2K\sqrt{2}$

$\frac{10 - 2}{\sqrt{2}} = 2K \sqrt{2}$

$\frac{8}{\sqrt{2}} = \frac{2K\sqrt{2}}{1}$

= 2k$\sqrt{2} \times \sqrt{2}$ = 8

2k $\sqrt{4}$ = 8

2k x 2 = 8

4k = 8

k = $\frac{8}{4}$

k = 2

Un = n(n² + 1)

U⁵ = 5(² + 1)

= 5(25 + 1)

= 5(26) = 130

U⁴ = 4(4² + 1) = 4(16 + 1)

= 4(17) = 68

U5 - U4 = 130 - 68

= 62

$\frac{1\frac{7}{8} \times 2\frac{2}{5}}{6\frac{3}{4} \div \frac{3}{4}}$

from numerator $1 \frac{7}{8} \times 2 \frac{2}{5}$

= $\frac{15}{8} \times \frac{12}{5}$

= $\frac{3 \times 3}{2 \times 1} = \frac{9}{2}$

from denominator $6\frac{3}{4} \div \frac{3}{4}$

= $\frac{27}{4} \div \frac{3}{4}$

= $\frac{27}{4} \times \frac{4}{3}$

= $\frac{9 \times 1}{1 \times 1} = \frac{9}{1}$

$\frac{9}{2} \div \frac{9}{1} = \frac{9}{2} \times \frac{1}{9}$

= $\frac{1}{2}$

No explanation has been provided for this answer.