If Adam buys 3 marbles and 4 stickers, it costs $44.50.
If Adam buys 4 marbles and 3 stickers, he will need another $1.30.
- 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 = 44.50 --- (1)
4 marbles + 3 stickers = 44.50 + 1.30 = 45.80 --- (2)
(1) + (2)
7 marbles + 7 stickers = 90.30 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 90.30 ÷ 7 = 12.90 --- (4)
Cost of 1 marble and 1 sticker = $12.90
(b)
4 marbles + 3 stickers = 45.80 --- (2)
(4)
x 3 3 marbles + 3 stickers = 3 x 12.90 = 38.70 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 45.80 - 38.70
4 marbles - 3 marbles + 3 stickers - 3 stickers = 7.10
1 marble = 7.10
Cost of 1 marble = $7.10
(c)
Substitute 1 marble = 7.10 into (4).
1 marble + 1 sticker = 12.90
7.10 + 1 sticker = 12.90
1 sticker = 12.90 - 7.10 = 5.80
Cost of 1 sticker = $5.80
Answer(s): (a) $12.90; (b) $7.10; (c) $5.80