If Adam buys 3 marbles and 4 stickers, it costs $37.50.
If Adam buys 4 marbles and 3 stickers, he will need another $4.10.
- 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 = 37.50 --- (1)
4 marbles + 3 stickers = 37.50 + 4.10 = 41.60 --- (2)
(1) + (2)
7 marbles + 7 stickers = 79.10 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 79.10 ÷ 7 = 11.30 --- (4)
Cost of 1 marble and 1 sticker = $11.30
(b)
4 marbles + 3 stickers = 41.60 --- (2)
(4)
x 3 3 marbles + 3 stickers = 3 x 11.30 = 33.90 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 41.60 - 33.90
4 marbles - 3 marbles + 3 stickers - 3 stickers = 7.70
1 marble = 7.70
Cost of 1 marble = $7.70
(c)
Substitute 1 marble = 7.70 into (4).
1 marble + 1 sticker = 11.30
7.70 + 1 sticker = 11.30
1 sticker = 11.30 - 7.70 = 3.60
Cost of 1 sticker = $3.60
Answer(s): (a) $11.30; (b) $7.70; (c) $3.60