If Adam buys 3 marbles and 4 stickers, it costs $38.40.
If Adam buys 4 marbles and 3 stickers, he will need another $5.10.
- 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 = 38.40 --- (1)
4 marbles + 3 stickers = 38.40 + 5.10 = 43.50 --- (2)
(1) + (2)
7 marbles + 7 stickers = 81.90 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 81.90 ÷ 7 = 11.70 --- (4)
Cost of 1 marble and 1 sticker = $11.70
(b)
4 marbles + 3 stickers = 43.50 --- (2)
(4)
x 3 3 marbles + 3 stickers = 3 x 11.70 = 35.10 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 43.50 - 35.10
4 marbles - 3 marbles + 3 stickers - 3 stickers = 8.40
1 marble = 8.40
Cost of 1 marble = $8.40
(c)
Substitute 1 marble = 8.40 into (4).
1 marble + 1 sticker = 11.70
8.40 + 1 sticker = 11.70
1 sticker = 11.70 - 8.40 = 3.30
Cost of 1 sticker = $3.30
Answer(s): (a) $11.70; (b) $8.40; (c) $3.30