If Adam buys 4 marbles and 5 stickers, it costs $58.90.
If Adam buys 5 marbles and 4 stickers, he will need another $2.80.
- 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 = 58.90 --- (1)
5 marbles + 4 stickers = 58.90 + 2.80 = 61.70 --- (2)
(1) + (2)
9 marbles + 9 stickers = 120.60 --- (3)
(3)
÷ 9 1 marble + 1 sticker = 120.60 ÷ 9 = 13.40 --- (4)
Cost of 1 marble and 1 sticker = $13.40
(b)
5 marbles + 4 stickers = 61.70 --- (2)
(4)
x 4 4 marbles + 4 stickers = 4 x 13.40 = 53.60 --- (5)
(2) - (5)
5 marbles + 4 stickers - 4 marbles - 4 stickers = 61.70 - 53.60
5 marbles - 4 marbles + 4 stickers - 4 stickers = 8.10
1 marble = 8.10
Cost of 1 marble = $8.10
(c)
Substitute 1 marble = 8.10 into (4).
1 marble + 1 sticker = 13.40
8.10 + 1 sticker = 13.40
1 sticker = 13.40 - 8.10 = 5.30
Cost of 1 sticker = $5.30
Answer(s): (a) $13.40; (b) $8.10; (c) $5.30