Question

If the selling price of $10$ pens is equal to cost price of $14$ pens, find the gain percent.

Answer 1

S.P of $10$ pens $=$ C.P of $14$ pens $=Rs.100$ (Suppose)
$\therefore$ S.P of $1$ pen $=Rs.\frac{100}{10}=Rs.10$
and C.P of $1$ pen $=Rs.\frac{100}{14}=Rs.\frac{50}{7}$

$\therefore \text{Gain}=S.P-C.P$
$=Rs.10-Rs.\frac{50}{7}$
$=Rs.\frac{70-50}{7}$
$=Rs.\frac{20}{7}$

$\text{Gain}\%=\frac{\text{Gain}\times 100}{C.P}$

$=\frac{20\times 100\times 7}{7\times 50}$
$=40$

Hence, the required gain in percent is $40\%$.