If Adam buys 3 stickers and 4 marbles, it costs $42.20.
If Adam buys 4 stickers and 3 marbles, he will have $8.10 left.
- Find the cost of 1 sticker and 1 marble.
- Find the cost of 1 sticker.
- Find the cost of 1 marble.
(a)
3 stickers + 4 marbles = 42.20 --- (1)
4 stickers + 3 marbles = 42.20 - 8.10 = 34.10 --- (2)
(1) + (2)
7 stickers + 7 marbles = 76.30 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 76.30 ÷ 7 = 10.90 --- (4)
Cost of 1 sticker and 1 marble = $10.90
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 10.90 = 32.70 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 34.10 - 32.70
4 stickers - 3 stickers - 3 marbles + 3 marbles = 1.40
1 sticker = 1.40
Cost of 1 sticker = $1.40
(c)
Substitute 1 sticker = 1.40 into (4).
1 sticker + 1 marble = 10.90
1.40 + 1 marble = 10.90
1 marble = 10.90 - 1.40 = 9.50
Cost of 1 marble = $9.50
Answer(s): (a) $10.90; (b) $1.40; (c) $9.50