If Adam buys 4 marbles and 5 stickers, it costs $37.90.
If Adam buys 5 marbles and 4 stickers, he will have $5.60 left.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
4 marbles + 5 stickers = 37.90 --- (1)
5 marbles + 4 stickers = 37.90 - 5.60 = 32.30 --- (2)
(1) + (2)
9 marbles + 9 stickers = 70.20 --- (3)
(3)
÷ 9 1 marble + 1 sticker = 70.20 ÷ 9 = 7.80 --- (4)
Cost of 1 marble and 1 sticker = $7.80
(b)
(4)
x 4 4 marbles + 4 stickers = 4 x 7.80 = 31.20 --- (5)
(2) - (5)
5 marbles + 4 stickers - 4 marbles - 4 stickers = 32.30 - 31.20
5 marbles - 4 marbles - 4 stickers + 4 stickers = 1.10
1 marble = 1.10
Cost of 1 marble = $1.10
(c)
Substitute 1 marble = 1.10 into (4).
1 marble + 1 sticker = 7.80
1.10 + 1 sticker = 7.80
1 sticker = 7.80 - 1.10 = 6.70
Cost of 1 sticker = $6.70
Answer(s): (a) $7.80; (b) $1.10; (c) $6.70