If Adam buys 3 marbles and 4 stickers, it costs $36.80.
If Adam buys 4 marbles and 3 stickers, he will have $50 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 = 36.80 --- (1)
4 marbles + 3 stickers = 36.80 - 50 = 31.80 --- (2)
(1) + (2)
7 marbles + 7 stickers = 68.60 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 68.60 ÷ 7 = 9.80 --- (4)
Cost of 1 marble and 1 sticker = $9.80
(b)
(4)
x 3 3 marbles + 3 stickers = 3 x 9.80 = 29.40 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 31.80 - 29.40
4 marbles - 3 marbles - 3 stickers + 3 stickers = 2.40
1 marble = 2.40
Cost of 1 marble = $2.40
(c)
Substitute 1 marble = 2.40 into (4).
1 marble + 1 sticker = 9.80
2.40 + 1 sticker = 9.80
1 sticker = 9.80 - 2.40 = 7.40
Cost of 1 sticker = $7.40
Answer(s): (a) $9.80; (b) $2.40; (c) $7.40