5 marbles and 1 sticker cost $27.20.
1 marble and 5 stickers cost $25.60.
- 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)
5 marbles + 1 sticker = 27.20 --- (1)
1 marble + 5 stickers = 25.60 --- (2)
(1) + (2)
6 marbles + 6 stickers = 27.20 + 25.60
6 marbles + 6 stickers = 52.80 --- (3)
(3)
÷ 66 marbles + 6 stickers = 52.80
1 marble + 1 sticker = 52.80 ÷ 6
1 marble + 1 sticker = 8.80 --- (4)
(b)
(2) - (4)
(1 marble + 5 stickers) - (1 marble + 1 marble) = 25.60 - 8.80
1 marble - 1 marble + 5 stickers - 1 sticker = 16.80
4 stickers = 16.80
1 sticker = 16.80 ÷ 4 = 4.20
Cost of 1 sticker = $4.20
(c)
Substitute 1 sticker = 4.20 into (4).
1 marble + 1 sticker = 8.80
1 marble + 4.20 = 8.80
1 marble = 8.80 - 4.20 = 4.60
Cost of 1 marble = $4.60
(d)
(4)
x 9 1 marble + 1 sticker = 8.80
9 x (1 marble + 1 marble) = 9 x 8.80
9 marbles + 9 stickers = 79.20
Cost of 9 marbles and 9 stickers = $79.20
Answer(s): (a) $8.80; (b) $4.20; (c) $4.60; (d) $79.20