If Adam buys 4 stickers and 5 marbles, it costs $50.70.
If Adam buys 5 stickers and 4 marbles, he will need another $3.90.
- 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 = 50.70 --- (1)
5 stickers + 4 marbles = 50.70 + 3.90 = 54.60 --- (2)
(1) + (2)
9 stickers + 9 marbles = 105.30 --- (3)
(3)
÷ 9 1 sticker + 1 marble = 105.30 ÷ 9 = 11.70 --- (4)
Cost of 1 sticker and 1 marble = $11.70
(b)
5 stickers + 4 marbles = 54.60 --- (2)
(4)
x 4 4 stickers + 4 marbles = 4 x 11.70 = 46.80 --- (5)
(2) - (5)
5 stickers + 4 marbles - 4 stickers - 4 marbles = 54.60 - 46.80
5 stickers - 4 stickers + 4 marbles - 4 marbles = 7.80
1 sticker = 7.80
Cost of 1 sticker = $7.80
(c)
Substitute 1 sticker = 7.80 into (4).
1 sticker + 1 marble = 11.70
7.80 + 1 marble = 11.70
1 marble = 11.70 - 7.80 = 3.90
Cost of 1 marble = $3.90
Answer(s): (a) $11.70; (b) $7.80; (c) $3.90