2 stickers and 1 marble cost $7.40.
1 sticker and 2 marbles cost $10.30.
- 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 = 7.40 --- (1)
1 sticker + 2 marbles = 10.30 --- (2)
(1) + (2)
3 stickers + 3 marbles = 7.40 + 10.30
3 stickers + 3 marbles = 17.70 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 17.70
1 sticker + 1 marble = 17.70 ÷ 3
1 sticker + 1 marble = 5.90 --- (4)
Cost of 1 sticker and 1 marble = $5.90
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 10.30 - 5.90
1 sticker - 1 sticker + 2 marbles - 1 marble = 4.40
1 marble = 4.40
Cost of 1 marble = $4.40
(c)
Substitute 1 marble = 4.40 into (4).
1 sticker + 1 marble = 5.90
1 sticker + 4.40 = 5.90
1 sticker = 5.90 - 4.40 = 1.50
Cost of 1 sticker = $1.50
(d)
(4)
x 8 1 sticker + 1 marble = 5.90
8 x (1 sticker + 1 marble) = 8 x 5.90
8 stickers + 8 marbles = 47.20
Cost of 8 stickers and 8 marbles = $47.20
Answer(s): (a) $5.90; (b) $4.40; (c) $1.50; (d) $47.20