2 marbles and 1 sticker cost $4.50.
1 marble and 2 stickers cost $5.10.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 9 marbles and 9 stickers.
(a)
2 marbles + 1 sticker = 4.50 --- (1)
1 marble + 2 stickers = 5.10 --- (2)
(1) + (2)
3 marbles + 3 stickers = 4.50 + 5.10
3 marbles + 3 stickers = 9.60 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 9.60
1 marble + 1 sticker = 9.60 ÷ 3
1 marble + 1 sticker = 3.20 --- (4)
Cost of 1 marble and 1 sticker = $3.20
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 5.10 - 3.20
1 marble - 1 marble + 2 stickers - 1 sticker = 1.90
1 sticker = 1.90
Cost of 1 sticker = $1.90
(c)
Substitute 1 sticker = 1.90 into (4).
1 marble + 1 sticker = 3.20
1 marble + 1.90 = 3.20
1 marble = 3.20 - 1.90 = 1.30
Cost of 1 marble = $1.30
(d)
(4)
x 9 1 marble + 1 sticker = 3.20
9 x (1 marble + 1 marble) = 9 x 3.20
9 marbles + 9 stickers = 28.80
Cost of 9 marbles and 9 stickers = $28.80
Answer(s): (a) $3.20; (b) $1.90; (c) $1.30; (d) $28.80