If Adam buys 4 stickers and 5 marbles, it costs $59.70.
If Adam buys 5 stickers and 4 marbles, he will have $4.20 left.
- 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 = 59.70 --- (1)
5 stickers + 4 marbles = 59.70 - 4.20 = 55.50 --- (2)
(1) + (2)
9 stickers + 9 marbles = 115.20 --- (3)
(3)
÷ 9 1 sticker + 1 marble = 115.20 ÷ 9 = 12.80 --- (4)
Cost of 1 sticker and 1 marble = $12.80
(b)
(4)
x 4 4 stickers + 4 marbles = 4 x 12.80 = 51.20 --- (5)
(2) - (5)
5 stickers + 4 marbles - 4 stickers - 4 marbles = 55.50 - 51.20
5 stickers - 4 stickers - 4 marbles + 4 marbles = 4.30
1 sticker = 4.30
Cost of 1 sticker = $4.30
(c)
Substitute 1 sticker = 4.30 into (4).
1 sticker + 1 marble = 12.80
4.30 + 1 marble = 12.80
1 marble = 12.80 - 4.30 = 8.50
Cost of 1 marble = $8.50
Answer(s): (a) $12.80; (b) $4.30; (c) $8.50