math
posted by Joe .
Friendly's Clothing Store bought handkerchiefs, six for $10, and sold them 4 for $10. They made $60 profit. How many handkerchiefs did they sell?

unit purchase price = 10/6 = 1.6666..
unit selling price = 10/4 = 2.50
profit per unit = .833333
number sold = 60/.83333 = 72