If Adam buys 4 stickers and 5 marbles, it costs $56.90.
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 = 56.90 --- (1)
5 stickers + 4 marbles = 56.90 + 2.30 = 59.20 --- (2)
(1) + (2)
9 stickers + 9 marbles = 116.10 --- (3)
(3)
÷ 9 1 sticker + 1 marble = 116.10 ÷ 9 = 12.90 --- (4)
Cost of 1 sticker and 1 marble = $12.90
(b)
5 stickers + 4 marbles = 59.20 --- (2)
(4)
x 4 4 stickers + 4 marbles = 4 x 12.90 = 51.60 --- (5)
(2) - (5)
5 stickers + 4 marbles - 4 stickers - 4 marbles = 59.20 - 51.60
5 stickers - 4 stickers + 4 marbles - 4 marbles = 7.60
1 sticker = 7.60
Cost of 1 sticker = $7.60
(c)
Substitute 1 sticker = 7.60 into (4).
1 sticker + 1 marble = 12.90
7.60 + 1 marble = 12.90
1 marble = 12.90 - 7.60 = 5.30
Cost of 1 marble = $5.30
Answer(s): (a) $12.90; (b) $7.60; (c) $5.30