2 stickers and 1 marble cost $5.90.
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 8 stickers and 8 marbles.
(a)
2 stickers + 1 marble = 5.90 --- (1)
1 sticker + 2 marbles = 7.30 --- (2)
(1) + (2)
3 stickers + 3 marbles = 5.90 + 7.30
3 stickers + 3 marbles = 13.20 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 13.20
1 sticker + 1 marble = 13.20 ÷ 3
1 sticker + 1 marble = 4.40 --- (4)
Cost of 1 sticker and 1 marble = $4.40
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 7.30 - 4.40
1 sticker - 1 sticker + 2 marbles - 1 marble = 2.90
1 marble = 2.90
Cost of 1 marble = $2.90
(c)
Substitute 1 marble = 2.90 into (4).
1 sticker + 1 marble = 4.40
1 sticker + 2.90 = 4.40
1 sticker = 4.40 - 2.90 = 1.50
Cost of 1 sticker = $1.50
(d)
(4)
x 8 1 sticker + 1 marble = 4.40
8 x (1 sticker + 1 marble) = 8 x 4.40
8 stickers + 8 marbles = 35.20
Cost of 8 stickers and 8 marbles = $35.20
Answer(s): (a) $4.40; (b) $2.90; (c) $1.50; (d) $35.20