3 marbles and 1 sticker cost $16.60.
1 marble and 3 stickers cost $13.80.
- 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 = 16.60 --- (1)
1 marble + 3 stickers = 13.80 --- (2)
(1) + (2)
4 marbles + 4 stickers = 16.60 + 13.80
4 marbles + 4 stickers = 30.40 --- (3)
(3)
÷ 44 marbles + 4 stickers = 30.40
1 marble + 1 sticker = 30.40 ÷ 4
1 marble + 1 sticker = 7.60 --- (4)
(b)
(2) - (4)
(1 marble + 3 stickers) - (1 marble + 1 marble) = 13.80 - 7.60
1 marble - 1 marble + 3 stickers - 1 sticker = 6.20
2 stickers = 6.20
1 sticker = 6.20 ÷ 2 = 3.10
Cost of 1 sticker = $3.10
(c)
Substitute 1 sticker = 3.10 into (4).
1 marble + 1 sticker = 7.60
1 marble + 3.10 = 7.60
1 marble = 7.60 - 3.10 = 4.50
Cost of 1 marble = $4.50
(d)
(4)
x 7 1 marble + 1 sticker = 7.60
7 x (1 marble + 1 marble) = 7 x 7.60
7 marbles + 7 stickers = 53.20
Cost of 7 marbles and 7 stickers = $53.20
Answer(s): (a) $7.60; (b) $3.10; (c) $4.50; (d) $53.20