If Adam buys 4 marbles and 5 stickers, it costs $56.90.
If Adam buys 5 marbles and 4 stickers, he will need another $1.40.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
4 marbles + 5 stickers = 56.90 --- (1)
5 marbles + 4 stickers = 56.90 + 1.40 = 58.30 --- (2)
(1) + (2)
9 marbles + 9 stickers = 115.20 --- (3)
(3)
÷ 9 1 marble + 1 sticker = 115.20 ÷ 9 = 12.80 --- (4)
Cost of 1 marble and 1 sticker = $12.80
(b)
5 marbles + 4 stickers = 58.30 --- (2)
(4)
x 4 4 marbles + 4 stickers = 4 x 12.80 = 51.20 --- (5)
(2) - (5)
5 marbles + 4 stickers - 4 marbles - 4 stickers = 58.30 - 51.20
5 marbles - 4 marbles + 4 stickers - 4 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 = 12.80
7.10 + 1 sticker = 12.80
1 sticker = 12.80 - 7.10 = 5.70
Cost of 1 sticker = $5.70
Answer(s): (a) $12.80; (b) $7.10; (c) $5.70