2 stickers and 1 marble cost $11.50.
1 sticker and 2 marbles cost $11.90.
- 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 6 stickers and 6 marbles.
(a)
2 stickers + 1 marble = 11.50 --- (1)
1 sticker + 2 marbles = 11.90 --- (2)
(1) + (2)
3 stickers + 3 marbles = 11.50 + 11.90
3 stickers + 3 marbles = 23.40 --- (3)
(3)
÷ 3
3 stickers + 3 marbles = 23.40
1 sticker + 1 marble = 23.40 ÷ 3
1 sticker + 1 marble = 7.80 --- (4)
Cost of 1 sticker and 1 marble = $7.80
(b)
(2) - (4)
(1 sticker + 2 marbles) - (1 sticker + 1 marble) = 11.90 - 7.80
1 sticker - 1 sticker + 2 marbles - 1 marble = 4.10
1 marble = 4.10
Cost of 1 marble = $4.10
(c)
Substitute 1 marble = 4.10 into (4).
1 sticker + 1 marble = 7.80
1 sticker + 4.10 = 7.80
1 sticker = 7.80 - 4.10 = 3.70
Cost of 1 sticker = $3.70
(d)
(4)
x 6 1 sticker + 1 marble = 7.80
6 x (1 sticker + 1 marble) = 6 x 7.80
6 stickers + 6 marbles = 46.80
Cost of 6 stickers and 6 marbles = $46.80
Answer(s): (a) $7.80; (b) $4.10; (c) $3.70; (d) $46.80