A fruit seller sells mangoes at the rate of Rs.9 per kg and thereby loses 20%. At what price per kg, he should have sold them to make a profit of 5%?

A fruit seller sells mangoes of the rate of Rs 9, he is getting 20% loss

Hence, the  cost price is as below

$\begin{array}{rcl}x-0.2x& =& 9\\ 0.8x& =& 9\\ x& =& \frac{9}{0.8}\\ & =& 11.25\end{array}$

To get the profit of 5% the selling price is as below

$\begin{array}{rcl}SP& =& 11.25+0.05·\left(11.25\right)\\ & =& 11.25+0.5625\\ & =& 11.81\end{array}$