If Adam buys 5 marbles and 6 stickers, it costs $71.90.
If Adam buys 6 marbles and 5 stickers, he will have $6.30 left.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
5 marbles + 6 stickers = 71.90 --- (1)
6 marbles + 5 stickers = 71.90 - 6.30 = 65.60 --- (2)
(1) + (2)
11 marbles + 11 stickers = 137.50 --- (3)
(3)
÷ 11 1 marble + 1 sticker = 137.50 ÷ 11 = 12.50 --- (4)
Cost of 1 marble and 1 sticker = $12.50
(b)
(4)
x 5 5 marbles + 5 stickers = 5 x 12.50 = 62.50 --- (5)
(2) - (5)
6 marbles + 5 stickers - 5 marbles - 5 stickers = 65.60 - 62.50
6 marbles - 5 marbles - 5 stickers + 5 stickers = 3.10
1 marble = 3.10
Cost of 1 marble = $3.10
(c)
Substitute 1 marble = 3.10 into (4).
1 marble + 1 sticker = 12.50
3.10 + 1 sticker = 12.50
1 sticker = 12.50 - 3.10 = 9.40
Cost of 1 sticker = $9.40
Answer(s): (a) $12.50; (b) $3.10; (c) $9.40