3 marbles and 1 sticker cost $6.40.
1 marble and 3 stickers cost $7.20.
- 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 6 marbles and 6 stickers.
(a)
3 marbles + 1 sticker = 6.40 --- (1)
1 marble + 3 stickers = 7.20 --- (2)
(1) + (2)
4 marbles + 4 stickers = 6.40 + 7.20
4 marbles + 4 stickers = 13.60 --- (3)
(3)
÷ 44 marbles + 4 stickers = 13.60
1 marble + 1 sticker = 13.60 ÷ 4
1 marble + 1 sticker = 3.40 --- (4)
(b)
(2) - (4)
(1 marble + 3 stickers) - (1 marble + 1 marble) = 7.20 - 3.40
1 marble - 1 marble + 3 stickers - 1 sticker = 3.80
2 stickers = 3.80
1 sticker = 3.80 ÷ 2 = 1.90
Cost of 1 sticker = $1.90
(c)
Substitute 1 sticker = 1.90 into (4).
1 marble + 1 sticker = 3.40
1 marble + 1.90 = 3.40
1 marble = 3.40 - 1.90 = 1.50
Cost of 1 marble = $1.50
(d)
(4)
x 6 1 marble + 1 sticker = 3.40
6 x (1 marble + 1 marble) = 6 x 3.40
6 marbles + 6 stickers = 20.40
Cost of 6 marbles and 6 stickers = $20.40
Answer(s): (a) $3.40; (b) $1.90; (c) $1.50; (d) $20.40