3 marbles and 1 sticker cost $15.60.
1 marble and 3 stickers cost $10.80.
- 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)
3 marbles + 1 sticker = 15.60 --- (1)
1 marble + 3 stickers = 10.80 --- (2)
(1) + (2)
4 marbles + 4 stickers = 15.60 + 10.80
4 marbles + 4 stickers = 26.40 --- (3)
(3)
÷ 44 marbles + 4 stickers = 26.40
1 marble + 1 sticker = 26.40 ÷ 4
1 marble + 1 sticker = 6.60 --- (4)
(b)
(2) - (4)
(1 marble + 3 stickers) - (1 marble + 1 marble) = 10.80 - 6.60
1 marble - 1 marble + 3 stickers - 1 sticker = 4.20
2 stickers = 4.20
1 sticker = 4.20 ÷ 2 = 2.10
Cost of 1 sticker = $2.10
(c)
Substitute 1 sticker = 2.10 into (4).
1 marble + 1 sticker = 6.60
1 marble + 2.10 = 6.60
1 marble = 6.60 - 2.10 = 4.50
Cost of 1 marble = $4.50
(d)
(4)
x 9 1 marble + 1 sticker = 6.60
9 x (1 marble + 1 marble) = 9 x 6.60
9 marbles + 9 stickers = 59.40
Cost of 9 marbles and 9 stickers = $59.40
Answer(s): (a) $6.60; (b) $2.10; (c) $4.50; (d) $59.40