If Adam buys 3 stickers and 4 marbles, it costs $32.40.
If Adam buys 4 stickers and 3 marbles, he will have $60 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 = 32.40 --- (1)
4 stickers + 3 marbles = 32.40 - 60 = 26.40 --- (2)
(1) + (2)
7 stickers + 7 marbles = 58.80 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 58.80 ÷ 7 = 8.40 --- (4)
Cost of 1 sticker and 1 marble = $8.40
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 8.40 = 25.20 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 26.40 - 25.20
4 stickers - 3 stickers - 3 marbles + 3 marbles = 1.20
1 sticker = 1.20
Cost of 1 sticker = $1.20
(c)
Substitute 1 sticker = 1.20 into (4).
1 sticker + 1 marble = 8.40
1.20 + 1 marble = 8.40
1 marble = 8.40 - 1.20 = 7.20
Cost of 1 marble = $7.20
Answer(s): (a) $8.40; (b) $1.20; (c) $7.20