If Adam buys 3 stickers and 4 marbles, it costs $40.80.
If Adam buys 4 stickers and 3 marbles, he will need another $1.70.
- 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 = 40.80 --- (1)
4 stickers + 3 marbles = 40.80 + 1.70 = 42.50 --- (2)
(1) + (2)
7 stickers + 7 marbles = 83.30 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 83.30 ÷ 7 = 11.90 --- (4)
Cost of 1 sticker and 1 marble = $11.90
(b)
4 stickers + 3 marbles = 42.50 --- (2)
(4)
x 3 3 stickers + 3 marbles = 3 x 11.90 = 35.70 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 42.50 - 35.70
4 stickers - 3 stickers + 3 marbles - 3 marbles = 6.80
1 sticker = 6.80
Cost of 1 sticker = $6.80
(c)
Substitute 1 sticker = 6.80 into (4).
1 sticker + 1 marble = 11.90
6.80 + 1 marble = 11.90
1 marble = 11.90 - 6.80 = 5.10
Cost of 1 marble = $5.10
Answer(s): (a) $11.90; (b) $6.80; (c) $5.10