4 marbles and 1 sticker cost $15.20.
1 marble and 4 stickers cost $17.30.
- 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)
4 marbles + 1 sticker = 15.20 --- (1)
1 marble + 4 stickers = 17.30 --- (2)
(1) + (2)
5 marbles + 5 stickers = 15.20 + 17.30
5 marbles + 5 stickers = 32.50 --- (3)
(3)
÷ 55 marbles + 5 stickers = 32.50
1 marble + 1 sticker = 32.50 ÷ 5
1 marble + 1 sticker = 6.50 --- (4)
(b)
(2) - (4)
(1 marble + 4 stickers) - (1 marble + 1 marble) = 17.30 - 6.50
1 marble - 1 marble + 4 stickers - 1 sticker = 10.80
3 stickers = 10.80
1 sticker = 10.80 ÷ 3 = 3.60
Cost of 1 sticker = $3.60
(c)
Substitute 1 sticker = 3.60 into (4).
1 marble + 1 sticker = 6.50
1 marble + 3.60 = 6.50
1 marble = 6.50 - 3.60 = 2.90
Cost of 1 marble = $2.90
(d)
(4)
x 9 1 marble + 1 sticker = 6.50
9 x (1 marble + 1 marble) = 9 x 6.50
9 marbles + 9 stickers = 58.50
Cost of 9 marbles and 9 stickers = $58.50
Answer(s): (a) $6.50; (b) $3.60; (c) $2.90; (d) $58.50