WAEC 2018 · Paper 2 · Q1✱✱

(a)
A used car was purchased at ₦900,000.00. Its value depreciated by $30\%$ in the first year. In each subsequent year, the depreciation was $22\%$ of its value at the beginning of that year. If the car was bought on 1st March, 2011, calculate, correct to the nearest hundred naira, the value of the car on 28th February, 2015.

Worked solution (try it first)

After the first year the car has lost $30\%$ , so it is worth $70\%$ of ₦900,000: $0.7 \times 900\,000 = 630\,000$ , which is ₦630,000.
In each later year it loses $22\%$ of its value at the start of that year, so each year multiplies the value by $0.78$ .
1st March 2011 to 28th February 2015 is 4 full years: the first year, then 3 more.
Value $= 630\,000 \times 0.78^3$
$= 630\,000 \times 0.474552$
$\approx 298\,967.76$ , which is ₦299,000 to the nearest hundred naira.