By selling 100 oranges, a vendor gains a profit equal to the selling price of 20 oranges. Find his gain percent

Given :

By selling 100 oranges, a vendor gains a profit equal to the selling price of 20 oranges. 

To do :

We have to find the gain percent.

Solution :

Let the selling price of 1 orange be $Rs.\ 1$.

This implies,

The selling price of 100 oranges $= Rs.\ 100 \times1=Rs.\ 100$

Selling price of 25 oranges $= Rs.\ 25 \times 1= Rs.\ 25$

This implies,

Gain $=Rs.\ 25$

Cost price of 100 oranges $=$ Selling price of 100 oranges $-$ Gain

$= Rs.\ (100 - 25)$

$= Rs.\ 75$

Therefore,

Gain percent $= \frac{Gain}{Cost\ price}\times100 \%$

$= \frac{25}{75}\times100 \%$

$= \frac{100}{3} \%$

$= 33.33 \%$

The gain percent is $33.33 \%$.