A man sells 320 mangoes at the cost of 400 mangoes. His gain percent is:_________?

A. 10%
B. 15%
C. 20%
D. 25%
Explanation:
Let C.P of each mango = Rs. 1
C.P of 320 mangoes = Rs. 320
S.P of 320 mangoes = Rs. 400
Gain = (80/320 × 100)% = 25 %