2 marbles and 1 sticker cost $7.70.
1 marble and 2 stickers cost $9.10.
- 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 8 marbles and 8 stickers.
(a)
2 marbles + 1 sticker = 7.70 --- (1)
1 marble + 2 stickers = 9.10 --- (2)
(1) + (2)
3 marbles + 3 stickers = 7.70 + 9.10
3 marbles + 3 stickers = 16.80 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 16.80
1 marble + 1 sticker = 16.80 ÷ 3
1 marble + 1 sticker = 5.60 --- (4)
Cost of 1 marble and 1 sticker = $5.60
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 9.10 - 5.60
1 marble - 1 marble + 2 stickers - 1 sticker = 3.50
1 sticker = 3.50
Cost of 1 sticker = $3.50
(c)
Substitute 1 sticker = 3.50 into (4).
1 marble + 1 sticker = 5.60
1 marble + 3.50 = 5.60
1 marble = 5.60 - 3.50 = 2.10
Cost of 1 marble = $2.10
(d)
(4)
x 8 1 marble + 1 sticker = 5.60
8 x (1 marble + 1 marble) = 8 x 5.60
8 marbles + 8 stickers = 44.80
Cost of 8 marbles and 8 stickers = $44.80
Answer(s): (a) $5.60; (b) $3.50; (c) $2.10; (d) $44.80