Question:
Mark (✓) against the correct answer:
A number decreased by 30% gives 84. The number is
(a) 90
(b) 110
(c) 120
(d) 135
Solution:
(c) 120
Let the required number be $x$
$x-(30 \%$ of $x)=84$
$\Rightarrow\left\{x-\left(x \times \frac{30}{100}\right)\right\}=84$
$\Rightarrow\left(x-\frac{30 x}{100}\right)=84$
$\Rightarrow \frac{70 x}{100}=84$
$\Rightarrow x=\left(84 \times \frac{100}{70}\right)$
$\Rightarrow x=120$
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