Question

Tick (✓) the correct answer:
A number exceeds 20% of itself by 40. The number is
(a) 50
(b) 60
(c) 80
(d) 320

Answer 1

(a) 50

$$\begin{gathered} \mathrm{Let}x\mathrm{be}\mathrm{the}\mathrm{required}\mathrm{number}.\mathrm{Then},\mathrm{we}\mathrm{have}: \\ 20\%ofx+40=x \\ \Rightarrow \left(x\times \frac{20}{100}\right)+40=x \\ \Rightarrow \frac{20x}{100}+40=x \\ \Rightarrow \left(\frac{20x}{100}-x\right)=-40 \\ \Rightarrow \frac{-80x}{100}=-40 \\ \Rightarrow x=\left(40\times \frac{100}{80}\right) \\ \Rightarrow x=50 \end{gathered}$$