If Adam buys 4 stickers and 5 marbles, it costs $42.50.
If Adam buys 5 stickers and 4 marbles, he will need another $3.20.
- 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 = 42.50 --- (1)
5 stickers + 4 marbles = 42.50 + 3.20 = 45.70 --- (2)
(1) + (2)
9 stickers + 9 marbles = 88.20 --- (3)
(3)
÷ 9 1 sticker + 1 marble = 88.20 ÷ 9 = 9.80 --- (4)
Cost of 1 sticker and 1 marble = $9.80
(b)
5 stickers + 4 marbles = 45.70 --- (2)
(4)
x 4 4 stickers + 4 marbles = 4 x 9.80 = 39.20 --- (5)
(2) - (5)
5 stickers + 4 marbles - 4 stickers - 4 marbles = 45.70 - 39.20
5 stickers - 4 stickers + 4 marbles - 4 marbles = 6.50
1 sticker = 6.50
Cost of 1 sticker = $6.50
(c)
Substitute 1 sticker = 6.50 into (4).
1 sticker + 1 marble = 9.80
6.50 + 1 marble = 9.80
1 marble = 9.80 - 6.50 = 3.30
Cost of 1 marble = $3.30
Answer(s): (a) $9.80; (b) $6.50; (c) $3.30