If Adam buys 3 marbles and 4 stickers, it costs $41.70.
If Adam buys 4 marbles and 3 stickers, he will have $3.60 left.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
(a)
3 marbles + 4 stickers = 41.70 --- (1)
4 marbles + 3 stickers = 41.70 - 3.60 = 38.10 --- (2)
(1) + (2)
7 marbles + 7 stickers = 79.80 --- (3)
(3)
÷ 7 1 marble + 1 sticker = 79.80 ÷ 7 = 11.40 --- (4)
Cost of 1 marble and 1 sticker = $11.40
(b)
(4)
x 3 3 marbles + 3 stickers = 3 x 11.40 = 34.20 --- (5)
(2) - (5)
4 marbles + 3 stickers - 3 marbles - 3 stickers = 38.10 - 34.20
4 marbles - 3 marbles - 3 stickers + 3 stickers = 3.90
1 marble = 3.90
Cost of 1 marble = $3.90
(c)
Substitute 1 marble = 3.90 into (4).
1 marble + 1 sticker = 11.40
3.90 + 1 sticker = 11.40
1 sticker = 11.40 - 3.90 = 7.50
Cost of 1 sticker = $7.50
Answer(s): (a) $11.40; (b) $3.90; (c) $7.50