2 stickers and 1 marble cost $6.30.
1 sticker and 2 marbles cost $4.80.
- 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 = 6.30 --- (1)
1 sticker + 2 marbles = 4.80 --- (2)
(1) + (2)
3 stickers + 3 marbles = 6.30 + 4.80
3 stickers + 3 marbles = 11.10 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 11.10
1 sticker + 1 marble = 11.10 ÷ 3
1 sticker + 1 marble = 3.70 --- (4)
Cost of 1 sticker and 1 marble = $3.70
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 4.80 - 3.70
1 sticker - 1 sticker + 2 marbles - 1 marble = 1.10
1 marble = 1.10
Cost of 1 marble = $1.10
(c)
Substitute 1 marble = 1.10 into (4).
1 sticker + 1 marble = 3.70
1 sticker + 1.10 = 3.70
1 sticker = 3.70 - 1.10 = 2.60
Cost of 1 sticker = $2.60
(d)
(4)
x 8 1 sticker + 1 marble = 3.70
8 x (1 sticker + 1 marble) = 8 x 3.70
8 stickers + 8 marbles = 29.60
Cost of 8 stickers and 8 marbles = $29.60
Answer(s): (a) $3.70; (b) $1.10; (c) $2.60; (d) $29.60