2 marbles and 1 sticker cost $8.10.
1 marble and 2 stickers cost $8.40.
- 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 = 8.10 --- (1)
1 marble + 2 stickers = 8.40 --- (2)
(1) + (2)
3 marbles + 3 stickers = 8.10 + 8.40
3 marbles + 3 stickers = 16.50 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 16.50
1 marble + 1 sticker = 16.50 ÷ 3
1 marble + 1 sticker = 5.50 --- (4)
Cost of 1 marble and 1 sticker = $5.50
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 8.40 - 5.50
1 marble - 1 marble + 2 stickers - 1 sticker = 2.90
1 sticker = 2.90
Cost of 1 sticker = $2.90
(c)
Substitute 1 sticker = 2.90 into (4).
1 marble + 1 sticker = 5.50
1 marble + 2.90 = 5.50
1 marble = 5.50 - 2.90 = 2.60
Cost of 1 marble = $2.60
(d)
(4)
x 9 1 marble + 1 sticker = 5.50
9 x (1 marble + 1 marble) = 9 x 5.50
9 marbles + 9 stickers = 49.50
Cost of 9 marbles and 9 stickers = $49.50
Answer(s): (a) $5.50; (b) $2.90; (c) $2.60; (d) $49.50