Adam pays $31.70 for 1 marble and 8 stickers.
The marble costs $2.90 more than each sticker.
- What is the cost of 1 marble?
- How much is the cost of 8 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 + 2.90
Cost of 8 stickers
= 8 x 1 u
= 8 u
Total cost of 1 marble and 8 stickers
= 1 u + 2.90 + 8 u
= 9 u + 2.90
9 u + 2.90 = 31.70
9 u = 31.70 - 2.90
9 u = 28.80
1 u = 28.80 ÷ 9 = 3.20
Cost of 1 marble
= 3.20 + 2.90
= $6.10
(b)
Cost of 8 marbles and 7 stickers
= 8 x 6.10 + 7 x 3.20
= 48.80 + 22.40
= $71.20
Answer(s): (a) $6.10; (b) $71.20