WAEC Mathematics Past Questions & Answers - Page 131

%Zinc + %Copper = 100%

65% + %Copper = 100%

%Copper = 100% - 65% = 35%

%Copper = $\frac{\text{Mass of % Copper}}{\text{Mass of Casting}}$ x 100%

Mass of Casting = $\frac{147}{35}$ x 100%

= 420g

Let the no. be x and x + 1

x + (x + 1) = $\frac{5}{6}$ of x(x + 1)

2x + 1 = $\frac{5}{6}$ x(x + 1)

6(2x + 1) = 5x² + 5x

12x + 6 = 5x² + 5x

5x² + 5x - 12x - 6 = 0

5x² - 7x - 6 = 0

5x² - 10x + 3x - 6 = 0

5x(x - 2) + 3(x - 2) = 0

(5x + 3)(x - 2) = 0

(5x + 3)(x - 2) = 0

(5x + 3) = 0

x - 2 = 0

for (5x + 3) = 0

5x = -3

x = $\frac{-3}{5}$ (Imposible since x is a whole number)

x - 2 = 0

x = 2

x = $\frac{-3}{5}$(Impossible since x is a whole number)

x - 2 = 0

x = 2

The numbers are x = 2

x + 1 = 2 + 1

= 3

1$\frac{1}{2} + 2\frac{1}{3} \times \frac{3}{4} - \frac{1}{2}$

$\frac{3}{2} + \frac{7}{3} \times \frac{3}{4} - \frac{1}{2} = \frac{3}{2} + \frac{7}{4} - \frac{1}{2}$

= $\frac{6 + 7 - 2}{4} = \frac{11}{4}$

= 2$\frac{3}{4}$

No explanation has been provided for this answer.

1 litre = N63.00

xlitres = N900.00

x x N63 = N900 x 1 litre

x = $\frac{900}{63} \times litre$

x = $\frac{100}{7}$ litres

Also, 1 litre = 14km

$\frac{100}{7}$ = y

y x 1 litre = $\frac{100litre}{7}$ x 14km

y = 20km