If Adam buys 4 stickers and 5 marbles, it costs $560.
If Adam buys 5 stickers and 4 marbles, he will need another $2.30.
- Find the cost of 1 sticker and 1 marble.
- Find the cost of 1 sticker.
- Find the cost of 1 marble.
(a)
4 stickers + 5 marbles = 560 --- (1)
5 stickers + 4 marbles = 560 + 2.30 = 58.30 --- (2)
(1) + (2)
9 stickers + 9 marbles = 114.30 --- (3)
(3)
÷ 9 1 sticker + 1 marble = 114.30 ÷ 9 = 12.70 --- (4)
Cost of 1 sticker and 1 marble = $12.70
(b)
5 stickers + 4 marbles = 58.30 --- (2)
(4)
x 4 4 stickers + 4 marbles = 4 x 12.70 = 50.80 --- (5)
(2) - (5)
5 stickers + 4 marbles - 4 stickers - 4 marbles = 58.30 - 50.80
5 stickers - 4 stickers + 4 marbles - 4 marbles = 7.50
1 sticker = 7.50
Cost of 1 sticker = $7.50
(c)
Substitute 1 sticker = 7.50 into (4).
1 sticker + 1 marble = 12.70
7.50 + 1 marble = 12.70
1 marble = 12.70 - 7.50 = 5.20
Cost of 1 marble = $5.20
Answer(s): (a) $12.70; (b) $7.50; (c) $5.20