By selling 150 mangoes, a fruit-seller gains the selling price of 30 mangoes. Find the gain percent?

A. 20%
B. 25%
C. 18%
D. 30%
Explanation:
SP = CP + g
150 SP = 150 CP + 30 SP
120 SP = 150 CP
120 — 30 CP
100 — ? => 25%