If Adam buys 3 marbles and 4 stickers, it costs $33.80.
If Adam buys 4 marbles and 3 stickers, he will have $5.30 left.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
3 marbles + 4 stickers = 33.80 --- (1)
4 marbles + 3 stickers = 33.80 - 5.30 = 28.50 --- (2)
(1) + (2)
7 marbles + 7 stickers = 62.30 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 62.30 ÷ 7 = 8.90 --- (4)
Cost of 1 marble and 1 sticker = $8.90
(b)
(4)
x 3 3 marbles + 3 stickers = 3 x 8.90 = 26.70 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 28.50 - 26.70
4 marbles - 3 marbles - 3 stickers + 3 stickers = 1.80
1 marble = 1.80
Cost of 1 marble = $1.80
(c)
Substitute 1 marble = 1.80 into (4).
1 marble + 1 sticker = 8.90
1.80 + 1 sticker = 8.90
1 sticker = 8.90 - 1.80 = 7.10
Cost of 1 sticker = $7.10
Answer(s): (a) $8.90; (b) $1.80; (c) $7.10