2 stickers and 1 marble cost $8.90.
1 sticker and 2 marbles cost $6.40.
- 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 = 8.90 --- (1)
1 sticker + 2 marbles = 6.40 --- (2)
(1) + (2)
3 stickers + 3 marbles = 8.90 + 6.40
3 stickers + 3 marbles = 15.30 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 15.30
1 sticker + 1 marble = 15.30 ÷ 3
1 sticker + 1 marble = 5.10 --- (4)
Cost of 1 sticker and 1 marble = $5.10
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 6.40 - 5.10
1 sticker - 1 sticker + 2 marbles - 1 marble = 1.30
1 marble = 1.30
Cost of 1 marble = $1.30
(c)
Substitute 1 marble = 1.30 into (4).
1 sticker + 1 marble = 5.10
1 sticker + 1.30 = 5.10
1 sticker = 5.10 - 1.30 = 3.80
Cost of 1 sticker = $3.80
(d)
(4)
x 6 1 sticker + 1 marble = 5.10
6 x (1 sticker + 1 marble) = 6 x 5.10
6 stickers + 6 marbles = 30.60
Cost of 6 stickers and 6 marbles = $30.60
Answer(s): (a) $5.10; (b) $1.30; (c) $3.80; (d) $30.60