Question:
On selling an article for Rs 48, a shopkeeper loses 20%. In order to gain 20%, what would be the selling price?
(a) Rs 52
(b) Rs 56
(c) Rs 68
(d) Rs 72
Solution:
(d) Rs 72
$\mathrm{SP}=\mathrm{Rs} 48$
Loss $=20 \%$
Now, $\mathrm{CP}=\frac{100}{100-\text { loss } \%} \times \mathrm{SP}$
$=\operatorname{Rs}\left(\frac{100}{(100-\text { loss } \%)} \times \mathrm{SP}\right)$
$=\operatorname{Rs}\left(\frac{100}{(100-20)} \times 48\right)$
$=\operatorname{Rs}\left(\frac{100}{80} \times 48\right)$
$=\operatorname{Rs} 60$
$\therefore$ Desired SP $=\left\{\frac{(100+\text { gain } \%)}{100} \times \mathrm{CP}\right\}$
$=\left\{\frac{(100+20)}{100} \times 60\right\}$
$=\operatorname{Rs}\left(\frac{12}{10} \times 60\right)$
$=\operatorname{Rs} 72$