Gwen paid $420 for some wafers and cookies. The ratio of the boxes of wafers to the boxes of cookies was 3 : 5. Each box of wafers cost $15 more than each box of cookies. She paid $120 more for the wafers than the cookies. What was the price of each box of wafers?
(a)
Total amount that the cookies cost
= (420 - 120) ÷ 2
= 300 ÷ 2
= $150

Total amount that the wafers cost
= 150 + 120
= $270

Number of sets of wafers = 3
Number of sets of cookies = 5

Cost of 1 set of wafers
= 270 ÷ 3
= $90

Cost of 1 set of cookies
= 150 ÷ 5
= $30

Amount that 1 set of wafers cost more than 1 set of cookies
= 90 - 30
= $60

Number of boxes of wafers in 1 set
= 60 ÷ 15
= 4

Price of each box of wafers
= 90 ÷ 4
= $22.50

Answer(s): $22.50