If Adam buys 4 marbles and 5 stickers, it costs $570.
If Adam buys 5 marbles and 4 stickers, he will need another $2.10.
- 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 = 570 --- (1)
5 marbles + 4 stickers = 570 + 2.10 = 59.10 --- (2)
(1) + (2)
9 marbles + 9 stickers = 116.10 --- (3)
(3)
÷ 9 1 marble + 1 sticker = 116.10 ÷ 9 = 12.90 --- (4)
Cost of 1 marble and 1 sticker = $12.90
(b)
5 marbles + 4 stickers = 59.10 --- (2)
(4)
x 4 4 marbles + 4 stickers = 4 x 12.90 = 51.60 --- (5)
(2) - (5)
5 marbles + 4 stickers - 4 marbles - 4 stickers = 59.10 - 51.60
5 marbles - 4 marbles + 4 stickers - 4 stickers = 7.50
1 marble = 7.50
Cost of 1 marble = $7.50
(c)
Substitute 1 marble = 7.50 into (4).
1 marble + 1 sticker = 12.90
7.50 + 1 sticker = 12.90
1 sticker = 12.90 - 7.50 = 5.40
Cost of 1 sticker = $5.40
Answer(s): (a) $12.90; (b) $7.50; (c) $5.40