Question

the selling price of 12 pens is equal to the cost prize of 15 pens . find the gain percent

Answer 1

Let CP of 1 pen =100
CP of 15 pen = 1500
SP of 12 pen = 1500
SP of 1 pen = 1500/12=125
Profit = 125 -100=25 rs
gain %= (25/100)×100=25%

Answer 2

let cp of 15 pens be x
and sp of 12 pens be y
gain%=x-y/y×100
= (15-12/12×100)%
=(3/12×100)%
=25%