If Adam buys 3 stickers and 4 marbles, it costs $41.70.
If Adam buys 4 stickers and 3 marbles, he will need another $3.40.
- Find the cost of 1 sticker and 1 marble.
- Find the cost of 1 sticker.
- Find the cost of 1 marble.
(a)
3 stickers + 4 marbles = 41.70 --- (1)
4 stickers + 3 marbles = 41.70 + 3.40 = 45.10 --- (2)
(1) + (2)
7 stickers + 7 marbles = 86.80 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 86.80 ÷ 7 = 12.40 --- (4)
Cost of 1 sticker and 1 marble = $12.40
(b)
4 stickers + 3 marbles = 45.10 --- (2)
(4)
x 3 3 stickers + 3 marbles = 3 x 12.40 = 37.20 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 45.10 - 37.20
4 stickers - 3 stickers + 3 marbles - 3 marbles = 7.90
1 sticker = 7.90
Cost of 1 sticker = $7.90
(c)
Substitute 1 sticker = 7.90 into (4).
1 sticker + 1 marble = 12.40
7.90 + 1 marble = 12.40
1 marble = 12.40 - 7.90 = 4.50
Cost of 1 marble = $4.50
Answer(s): (a) $12.40; (b) $7.90; (c) $4.50