Adam pays $39.90 for 1 marble and 6 stickers.
The marble costs $2.10 more than each sticker.
- What is the cost of 1 marble?
- How much is the cost of 6 marbles and 7 stickers?
(a)
Choose the cheaper item to be 1 u.
Cost of 1 sticker = 1 u
Cost of 1 marble = 1 u + 2.10
Cost of 6 stickers
= 6 x 1 u
= 6 u
Total cost of 1 marble and 6 stickers
= 1 u + 2.10 + 6 u
= 7 u + 2.10
7 u + 2.10 = 39.90
7 u = 39.90 - 2.10
7 u = 37.80
1 u = 37.80 ÷ 7 = 5.40
Cost of 1 marble
= 5.40 + 2.10
= $7.50
(b)
Cost of 6 marbles and 7 stickers
= 6 x 7.50 + 7 x 5.40
= 45.00 + 37.80
= $82.80
Answer(s): (a) $7.50; (b) $82.80