If Adam buys 3 marbles and 4 stickers, it costs $42.50.
If Adam buys 4 marbles and 3 stickers, he will need another $1.10.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
3 marbles + 4 stickers = 42.50 --- (1)
4 marbles + 3 stickers = 42.50 + 1.10 = 43.60 --- (2)
(1) + (2)
7 marbles + 7 stickers = 86.10 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 86.10 ÷ 7 = 12.30 --- (4)
Cost of 1 marble and 1 sticker = $12.30
(b)
4 marbles + 3 stickers = 43.60 --- (2)
(4)
x 3 3 marbles + 3 stickers = 3 x 12.30 = 36.90 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 43.60 - 36.90
4 marbles - 3 marbles + 3 stickers - 3 stickers = 6.70
1 marble = 6.70
Cost of 1 marble = $6.70
(c)
Substitute 1 marble = 6.70 into (4).
1 marble + 1 sticker = 12.30
6.70 + 1 sticker = 12.30
1 sticker = 12.30 - 6.70 = 5.60
Cost of 1 sticker = $5.60
Answer(s): (a) $12.30; (b) $6.70; (c) $5.60