If Adam buys 3 stickers and 4 marbles, it costs $56.40.
If Adam buys 4 stickers and 3 marbles, he will have $4.30 left.
- 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 = 56.40 --- (1)
4 stickers + 3 marbles = 56.40 - 4.30 = 52.10 --- (2)
(1) + (2)
7 stickers + 7 marbles = 108.50 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 108.50 ÷ 7 = 15.50 --- (4)
Cost of 1 sticker and 1 marble = $15.50
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 15.50 = 46.50 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 52.10 - 46.50
4 stickers - 3 stickers - 3 marbles + 3 marbles = 5.60
1 sticker = 5.60
Cost of 1 sticker = $5.60
(c)
Substitute 1 sticker = 5.60 into (4).
1 sticker + 1 marble = 15.50
5.60 + 1 marble = 15.50
1 marble = 15.50 - 5.60 = 9.90
Cost of 1 marble = $9.90
Answer(s): (a) $15.50; (b) $5.60; (c) $9.90