2 marbles and 1 sticker cost $6.50.
1 marble and 2 stickers cost $4.90.
- 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 8 marbles and 8 stickers.
(a)
2 marbles + 1 sticker = 6.50 --- (1)
1 marble + 2 stickers = 4.90 --- (2)
(1) + (2)
3 marbles + 3 stickers = 6.50 + 4.90
3 marbles + 3 stickers = 11.40 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 11.40
1 marble + 1 sticker = 11.40 ÷ 3
1 marble + 1 sticker = 3.80 --- (4)
Cost of 1 marble and 1 sticker = $3.80
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 4.90 - 3.80
1 marble - 1 marble + 2 stickers - 1 sticker = 1.10
1 sticker = 1.10
Cost of 1 sticker = $1.10
(c)
Substitute 1 sticker = 1.10 into (4).
1 marble + 1 sticker = 3.80
1 marble + 1.10 = 3.80
1 marble = 3.80 - 1.10 = 2.70
Cost of 1 marble = $2.70
(d)
(4)
x 8 1 marble + 1 sticker = 3.80
8 x (1 marble + 1 marble) = 8 x 3.80
8 marbles + 8 stickers = 30.40
Cost of 8 marbles and 8 stickers = $30.40
Answer(s): (a) $3.80; (b) $1.10; (c) $2.70; (d) $30.40