If Adam buys 3 stickers and 4 marbles, it costs $45.40.
If Adam buys 4 stickers and 3 marbles, he will have $4.70 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 = 45.40 --- (1)
4 stickers + 3 marbles = 45.40 - 4.70 = 40.70 --- (2)
(1) + (2)
7 stickers + 7 marbles = 86.10 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 86.10 ÷ 7 = 12.30 --- (4)
Cost of 1 sticker and 1 marble = $12.30
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 12.30 = 36.90 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 40.70 - 36.90
4 stickers - 3 stickers - 3 marbles + 3 marbles = 3.80
1 sticker = 3.80
Cost of 1 sticker = $3.80
(c)
Substitute 1 sticker = 3.80 into (4).
1 sticker + 1 marble = 12.30
3.80 + 1 marble = 12.30
1 marble = 12.30 - 3.80 = 8.50
Cost of 1 marble = $8.50
Answer(s): (a) $12.30; (b) $3.80; (c) $8.50