If Adam buys 4 marbles and 5 stickers, it costs $56.80.
If Adam buys 5 marbles and 4 stickers, he will have $1.10 left.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
4 marbles + 5 stickers = 56.80 --- (1)
5 marbles + 4 stickers = 56.80 - 1.10 = 55.70 --- (2)
(1) + (2)
9 marbles + 9 stickers = 112.50 --- (3)
(3)
÷ 9 1 marble + 1 sticker = 112.50 ÷ 9 = 12.50 --- (4)
Cost of 1 marble and 1 sticker = $12.50
(b)
(4)
x 4 4 marbles + 4 stickers = 4 x 12.50 = 500 --- (5)
(2) - (5)
5 marbles + 4 stickers - 4 marbles - 4 stickers = 55.70 - 500
5 marbles - 4 marbles - 4 stickers + 4 stickers = 5.70
1 marble = 5.70
Cost of 1 marble = $5.70
(c)
Substitute 1 marble = 5.70 into (4).
1 marble + 1 sticker = 12.50
5.70 + 1 sticker = 12.50
1 sticker = 12.50 - 5.70 = 6.80
Cost of 1 sticker = $6.80
Answer(s): (a) $12.50; (b) $5.70; (c) $6.80