WAEC 2017 · Paper 2 · Q2

(a)
A trader invested some money in a bank for two years at $5\%$ per annum compound interest. If he collected an amount of ₦2,205,000.00 for his investment, calculate the money invested.
(b)
The area of a triangle is $30\text{ cm}^2$ . If the ratio of the height of the triangle to its base is $3 : 2$ , calculate, correct to two decimal places, the height of the triangle.

Worked solution (try it first)

(a)

Compound interest at $5\%$ for two years multiplies the money by $1.05^2 = 1.1025$ .
So $1.1025P = 2\,205\,000$ and $P = ₦2,000,000.00$ .

(b)

Height : base $= 3 : 2$ , so the base is $\frac23$ of the height: $b = \frac{2h}{3}$ .
Area: $\frac12 \times \frac{2h}{3} \times h = \frac{h^2}{3}$
$= 30$ , so $h^2 = 90$ and $h = \sqrt{90} \approx 9.49$ cm.

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