2 stickers and 1 marble cost $5.30.
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 4 stickers and 4 marbles.
(a)
2 stickers + 1 marble = 5.30 --- (1)
1 sticker + 2 marbles = 6.40 --- (2)
(1) + (2)
3 stickers + 3 marbles = 5.30 + 6.40
3 stickers + 3 marbles = 11.70 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 11.70
1 sticker + 1 marble = 11.70 ÷ 3
1 sticker + 1 marble = 3.90 --- (4)
Cost of 1 sticker and 1 marble = $3.90
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 6.40 - 3.90
1 sticker - 1 sticker + 2 marbles - 1 marble = 2.50
1 marble = 2.50
Cost of 1 marble = $2.50
(c)
Substitute 1 marble = 2.50 into (4).
1 sticker + 1 marble = 3.90
1 sticker + 2.50 = 3.90
1 sticker = 3.90 - 2.50 = 1.40
Cost of 1 sticker = $1.40
(d)
(4)
x 4 1 sticker + 1 marble = 3.90
4 x (1 sticker + 1 marble) = 4 x 3.90
4 stickers + 4 marbles = 15.60
Cost of 4 stickers and 4 marbles = $15.60
Answer(s): (a) $3.90; (b) $2.50; (c) $1.40; (d) $15.60