From Barrons:
A grocer buys apples for 63 cents per pound. If 10% of the apples go bad and he still wants to make a 20% profit over his purchase price, what should be the sales price?
I used numbers. I said that he bought 10 lbs for a total of $6.30. if 1lb goes bad, he has 9lbs to make $7.56 (6.30*120%). So 7.56/9 = .84
However, this is incorrect and I'd like to know why my logic is wrong. Thanks