2 marbles and 1 sticker cost $10.60.
1 marble and 2 stickers cost $11.90.
- 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 = 10.60 --- (1)
1 marble + 2 stickers = 11.90 --- (2)
(1) + (2)
3 marbles + 3 stickers = 10.60 + 11.90
3 marbles + 3 stickers = 22.50 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 22.50
1 marble + 1 sticker = 22.50 ÷ 3
1 marble + 1 sticker = 7.50 --- (4)
Cost of 1 marble and 1 sticker = $7.50
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 11.90 - 7.50
1 marble - 1 marble + 2 stickers - 1 sticker = 4.40
1 sticker = 4.40
Cost of 1 sticker = $4.40
(c)
Substitute 1 sticker = 4.40 into (4).
1 marble + 1 sticker = 7.50
1 marble + 4.40 = 7.50
1 marble = 7.50 - 4.40 = 3.10
Cost of 1 marble = $3.10
(d)
(4)
x 9 1 marble + 1 sticker = 7.50
9 x (1 marble + 1 marble) = 9 x 7.50
9 marbles + 9 stickers = 67.50
Cost of 9 marbles and 9 stickers = $67.50
Answer(s): (a) $7.50; (b) $4.40; (c) $3.10; (d) $67.50