If Adam buys 3 marbles and 4 stickers, it costs $38.70.
If Adam buys 4 marbles and 3 stickers, he will have $60 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 = 38.70 --- (1)
4 marbles + 3 stickers = 38.70 - 60 = 32.70 --- (2)
(1) + (2)
7 marbles + 7 stickers = 71.40 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 71.40 ÷ 7 = 10.20 --- (4)
Cost of 1 marble and 1 sticker = $10.20
(b)
(4)
x 3 3 marbles + 3 stickers = 3 x 10.20 = 30.60 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 32.70 - 30.60
4 marbles - 3 marbles - 3 stickers + 3 stickers = 2.10
1 marble = 2.10
Cost of 1 marble = $2.10
(c)
Substitute 1 marble = 2.10 into (4).
1 marble + 1 sticker = 10.20
2.10 + 1 sticker = 10.20
1 sticker = 10.20 - 2.10 = 8.10
Cost of 1 sticker = $8.10
Answer(s): (a) $10.20; (b) $2.10; (c) $8.10