2 stickers and 1 marble cost $6.80.
1 sticker and 2 marbles cost $7.30.
- Find the cost of 1 sticker and 1 marble.
- Find the cost of 1 marble.
- Find the cost of 1 sticker.
- Find the cost of 6 stickers and 6 marbles.
(a)
2 stickers + 1 marble = 6.80 --- (1)
1 sticker + 2 marbles = 7.30 --- (2)
(1) + (2)
3 stickers + 3 marbles = 6.80 + 7.30
3 stickers + 3 marbles = 14.10 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 14.10
1 sticker + 1 marble = 14.10 ÷ 3
1 sticker + 1 marble = 4.70 --- (4)
Cost of 1 sticker and 1 marble = $4.70
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 7.30 - 4.70
1 sticker - 1 sticker + 2 marbles - 1 marble = 2.60
1 marble = 2.60
Cost of 1 marble = $2.60
(c)
Substitute 1 marble = 2.60 into (4).
1 sticker + 1 marble = 4.70
1 sticker + 2.60 = 4.70
1 sticker = 4.70 - 2.60 = 2.10
Cost of 1 sticker = $2.10
(d)
(4)
x 6 1 sticker + 1 marble = 4.70
6 x (1 sticker + 1 marble) = 6 x 4.70
6 stickers + 6 marbles = 28.20
Cost of 6 stickers and 6 marbles = $28.20
Answer(s): (a) $4.70; (b) $2.60; (c) $2.10; (d) $28.20