If Adam buys 3 stickers and 4 marbles, it costs $42.60.
If Adam buys 4 stickers and 3 marbles, he will have $3.30 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 = 42.60 --- (1)
4 stickers + 3 marbles = 42.60 - 3.30 = 39.30 --- (2)
(1) + (2)
7 stickers + 7 marbles = 81.90 --- (3)
(3)
÷ 7 1 sticker + 1 marble = 81.90 ÷ 7 = 11.70 --- (4)
Cost of 1 sticker and 1 marble = $11.70
(b)
(4)
x 3 3 stickers + 3 marbles = 3 x 11.70 = 35.10 --- (5)
(2) - (5)
4 stickers + 3 marbles - 3 stickers - 3 marbles = 39.30 - 35.10
4 stickers - 3 stickers - 3 marbles + 3 marbles = 4.20
1 sticker = 4.20
Cost of 1 sticker = $4.20
(c)
Substitute 1 sticker = 4.20 into (4).
1 sticker + 1 marble = 11.70
4.20 + 1 marble = 11.70
1 marble = 11.70 - 4.20 = 7.50
Cost of 1 marble = $7.50
Answer(s): (a) $11.70; (b) $4.20; (c) $7.50