2 marbles and 1 sticker cost $10.70.
1 marble and 2 stickers cost $8.50.
- 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 7 marbles and 7 stickers.
(a)
2 marbles + 1 sticker = 10.70 --- (1)
1 marble + 2 stickers = 8.50 --- (2)
(1) + (2)
3 marbles + 3 stickers = 10.70 + 8.50
3 marbles + 3 stickers = 19.20 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 19.20
1 marble + 1 sticker = 19.20 ÷ 3
1 marble + 1 sticker = 6.40 --- (4)
Cost of 1 marble and 1 sticker = $6.40
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 8.50 - 6.40
1 marble - 1 marble + 2 stickers - 1 sticker = 2.10
1 sticker = 2.10
Cost of 1 sticker = $2.10
(c)
Substitute 1 sticker = 2.10 into (4).
1 marble + 1 sticker = 6.40
1 marble + 2.10 = 6.40
1 marble = 6.40 - 2.10 = 4.30
Cost of 1 marble = $4.30
(d)
(4)
x 7 1 marble + 1 sticker = 6.40
7 x (1 marble + 1 marble) = 7 x 6.40
7 marbles + 7 stickers = 44.80
Cost of 7 marbles and 7 stickers = $44.80
Answer(s): (a) $6.40; (b) $2.10; (c) $4.30; (d) $44.80