If Adam buys 3 stickers and 4 marbles, it costs $35.50.
If Adam buys 4 stickers and 3 marbles, he will have $3.80 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 = 35.50 --- (1)
4 stickers + 3 marbles = 35.50 - 3.80 = 31.70 --- (2)
(1) + (2)
7 stickers + 7 marbles = 67.20 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 67.20 ÷ 7 = 9.60 --- (4)
Cost of 1 sticker and 1 marble = $9.60
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 9.60 = 28.80 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 31.70 - 28.80
4 stickers - 3 stickers - 3 marbles + 3 marbles = 2.90
1 sticker = 2.90
Cost of 1 sticker = $2.90
(c)
Substitute 1 sticker = 2.90 into (4).
1 sticker + 1 marble = 9.60
2.90 + 1 marble = 9.60
1 marble = 9.60 - 2.90 = 6.70
Cost of 1 marble = $6.70
Answer(s): (a) $9.60; (b) $2.90; (c) $6.70