30 apples = 100paise
he want 20% profit from 100 paise
20% profit in 100 paise is 20 paise
so now he planned to sell 30 apples for 100+20=120 paise
now the rate of 1 apple =120/30=4paise
for 100 paise =100/4=25.

cost of one apple is 1\30 i.e.0.033
now he wants to earns 20% profit
cost of one apple now .033*20\100
=.033 ( cost)+.0066(profit per apple )
=.0396
selling cost of one apple = .0396

25
explanation:
let s.p of 'x' apples=100p
20%profit
also,SP = 1.20 OF CP
THEREFORE,CP of 'x' apples = 100/1.20=83.3333p
COST OF 1 APPLE=3.33p(30 apples in 100p)
no. of apples bought in 83.33p=(83.33/3.33)=25

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