Last week he bought three apples for $3.90. The cost of an apple = 3.9/3 = 1.3 This week he bought 2 more apples which totals 5 for $6.50 The cost of each apple = 6.5/5 = 1.3. The cost of an apple in the two weeks is the same. Arnold bought more apples in the following week but there was a corresponding raise in price. When he bought fewer apples last week he never had to pay as much as he did the year later
