2 stickers and 1 marble cost $5.90.
1 sticker and 2 marbles cost $7.90.
- 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 = 5.90 --- (1)
1 sticker + 2 marbles = 7.90 --- (2)
(1) + (2)
3 stickers + 3 marbles = 5.90 + 7.90
3 stickers + 3 marbles = 13.80 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 13.80
1 sticker + 1 marble = 13.80 ÷ 3
1 sticker + 1 marble = 4.60 --- (4)
Cost of 1 sticker and 1 marble = $4.60
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 7.90 - 4.60
1 sticker - 1 sticker + 2 marbles - 1 marble = 3.30
1 marble = 3.30
Cost of 1 marble = $3.30
(c)
Substitute 1 marble = 3.30 into (4).
1 sticker + 1 marble = 4.60
1 sticker + 3.30 = 4.60
1 sticker = 4.60 - 3.30 = 1.30
Cost of 1 sticker = $1.30
(d)
(4)
x 4 1 sticker + 1 marble = 4.60
4 x (1 sticker + 1 marble) = 4 x 4.60
4 stickers + 4 marbles = 18.40
Cost of 4 stickers and 4 marbles = $18.40
Answer(s): (a) $4.60; (b) $3.30; (c) $1.30; (d) $18.40