By selling 90 balls for Tk. 160 a person loses 20%. How many ball pens should be sold for Tk. 96 so as to have a profit of 20%?

Question: By selling 90 chocolets for Tk. 160 a person loses 20%. How many chocolets should be sold for Tk. 96 so as to have a profit of 20%?

Solution:
S.P of 90 chocolets = Tk. 160
C.P of 90 chocolets = Tk. {160×(100/80)}
= Tk. 200

Desired S.P of 90 chocolets = Tk. (120/100) × 200
= Tk. 240

For Tk. 240 chocolets sold = 90
For Tk. 96 chocolets sold = (90/240) × 96
= 36