2 stickers and 1 marble cost $9.20.
1 sticker and 2 marbles cost $9.70.
- 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 5 stickers and 5 marbles.
(a)
2 stickers + 1 marble = 9.20 --- (1)
1 sticker + 2 marbles = 9.70 --- (2)
(1) + (2)
3 stickers + 3 marbles = 9.20 + 9.70
3 stickers + 3 marbles = 18.90 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 18.90
1 sticker + 1 marble = 18.90 ÷ 3
1 sticker + 1 marble = 6.30 --- (4)
Cost of 1 sticker and 1 marble = $6.30
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 9.70 - 6.30
1 sticker - 1 sticker + 2 marbles - 1 marble = 3.40
1 marble = 3.40
Cost of 1 marble = $3.40
(c)
Substitute 1 marble = 3.40 into (4).
1 sticker + 1 marble = 6.30
1 sticker + 3.40 = 6.30
1 sticker = 6.30 - 3.40 = 2.90
Cost of 1 sticker = $2.90
(d)
(4)
x 5 1 sticker + 1 marble = 6.30
5 x (1 sticker + 1 marble) = 5 x 6.30
5 stickers + 5 marbles = 31.50
Cost of 5 stickers and 5 marbles = $31.50
Answer(s): (a) $6.30; (b) $3.40; (c) $2.90; (d) $31.50