Question

The cost price of $11$ pens is equal to the selling price of $10$ pens. Find the loss or gain percent.

Answer 1

Let S.P. of each pen be $x$.
S.P. of $10$ pens $=$ $10x$
S.P. of $11$ pens $=$ $11x$
Given : C.P. of $11$ pens $=$ S.P. of $10$ pens $=$ $10x$
Here, S.P. > C.P.
$\therefore$ Profit $=$ S.P. $-$ C.P.
$=11x-10x=x$
Profit % $=\frac{Profit}{C.P.}\times 100=\frac{x}{10x}\times 100=10$%.