A grocery dealer cheats to the extent of 10% while buying as well as selling by using false weight. What is his increase in the profit percentage = ?

Solution (By Examveda Team)

According to the question,
Cheats while buying = 10%
Cheats while selling = 10%
$$\eqalign{ & \therefore \left( {a + b + \frac{{ab}}{{100}}} \right)\% \cr & = 10 + 10 + \frac{{10 \times 10}}{{100}} \cr & = 20 + 1 \cr & = 21 \cr} $$
∴ Increase in profit % = 21%