A loss of $20\%$ is incurred when $6$ articles are sold for a rupee. To gain $20\%$ how many articles should be sold for a rupee?

The correct option is A: $4$
Given than, $SP=Re.1,Loss\%=20\%$

When there is loss of $20\%,$ then $SP=CP-20\%CP=0.8\times CP$

$1=0.8CP$ [$\because SP=Re1,$ given]

$CP=\frac{1}{0.8}=\frac{10}{8}=\frac{5}{4}$

$\therefore CP=\frac{5}{4}$

To gain $20$%, $SP=CP+20\%CP=1.2\times CP=\frac{120}{100}\times \frac{5}{4}=\frac{3}{2}$

$\Rightarrow SP=Rs.\frac{3}{2}=Rs.1.5$ [when we increase the selling price,there will be gain of $20\%$ on $6$ article]

For $Rs.\frac{3}{2}$ number of articles sold $=6$

For $Rs.1$ number of articles to be sold $=6\times \frac{2}{3}=4$ articles.