If Adam buys 3 marbles and 4 stickers, it costs $34.80.
If Adam buys 4 marbles and 3 stickers, he will need another $2.50.
- 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 = 34.80 --- (1)
4 marbles + 3 stickers = 34.80 + 2.50 = 37.30 --- (2)
(1) + (2)
7 marbles + 7 stickers = 72.10 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 72.10 ÷ 7 = 10.30 --- (4)
Cost of 1 marble and 1 sticker = $10.30
(b)
4 marbles + 3 stickers = 37.30 --- (2)
(4)
x 3 3 marbles + 3 stickers = 3 x 10.30 = 30.90 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 37.30 - 30.90
4 marbles - 3 marbles + 3 stickers - 3 stickers = 6.40
1 marble = 6.40
Cost of 1 marble = $6.40
(c)
Substitute 1 marble = 6.40 into (4).
1 marble + 1 sticker = 10.30
6.40 + 1 sticker = 10.30
1 sticker = 10.30 - 6.40 = 3.90
Cost of 1 sticker = $3.90
Answer(s): (a) $10.30; (b) $6.40; (c) $3.90