3 marbles and 1 sticker cost $8.60.
1 marble and 3 stickers cost $10.60.
- 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)
3 marbles + 1 sticker = 8.60 --- (1)
1 marble + 3 stickers = 10.60 --- (2)
(1) + (2)
4 marbles + 4 stickers = 8.60 + 10.60
4 marbles + 4 stickers = 19.20 --- (3)
(3)
÷ 44 marbles + 4 stickers = 19.20
1 marble + 1 sticker = 19.20 ÷ 4
1 marble + 1 sticker = 4.80 --- (4)
(b)
(2) - (4)
(1 marble + 3 stickers) - (1 marble + 1 marble) = 10.60 - 4.80
1 marble - 1 marble + 3 stickers - 1 sticker = 5.80
2 stickers = 5.80
1 sticker = 5.80 ÷ 2 = 2.90
Cost of 1 sticker = $2.90
(c)
Substitute 1 sticker = 2.90 into (4).
1 marble + 1 sticker = 4.80
1 marble + 2.90 = 4.80
1 marble = 4.80 - 2.90 = 1.90
Cost of 1 marble = $1.90
(d)
(4)
x 7 1 marble + 1 sticker = 4.80
7 x (1 marble + 1 marble) = 7 x 4.80
7 marbles + 7 stickers = 33.60
Cost of 7 marbles and 7 stickers = $33.60
Answer(s): (a) $4.80; (b) $2.90; (c) $1.90; (d) $33.60