Question

Mark (✓) against the correct answer:
A number decreased by 30% gives 84. The number is
(a) 90
(b) 110
(c) 120
(d) 135

Answer 1

(c) 120

$\mathrm{Let}\mathrm{the}\mathrm{required}\mathrm{number}\mathrm{be}x$
$$\begin{gathered} x-\left(30\%ofx\right)=84 \\ \Rightarrow \left\{x-\left(x\times \frac{30}{100}\right)\right\}=84 \\ \Rightarrow \left(x-\frac{30x}{100}\right)=84 \\ \Rightarrow \frac{70x}{100}=84 \\ \Rightarrow x=\left(84\times \frac{100}{70}\right) \\ \Rightarrow x=120 \end{gathered}$$