Adam pays $21.30 for 1 marble and 7 stickers.
The marble costs $2.10 more than each sticker.
- What is the cost of 1 marble?
- How much is the cost of 7 marbles and 8 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 7 stickers
= 7 x 1 u
= 7 u
Total cost of 1 marble and 7 stickers
= 1 u + 2.10 + 7 u
= 8 u + 2.10
8 u + 2.10 = 21.30
8 u = 21.30 - 2.10
8 u = 19.20
1 u = 19.20 ÷ 8 = 2.40
Cost of 1 marble
= 2.40 + 2.10
= $4.50
(b)
Cost of 7 marbles and 8 stickers
= 7 x 4.50 + 8 x 2.40
= 31.50 + 19.20
= $50.70
Answer(s): (a) $4.50; (b) $50.70