3 stickers and 1 marble cost $7.10.
1 sticker and 3 marbles cost $12.50.
- 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)
3 stickers + 1 marble = 7.10 --- (1)
1 sticker + 3 marbles = 12.50 --- (2)
(1) + (2)
4 stickers + 4 marbles = 7.10 + 12.50
4 stickers + 4 marbles = 19.60 --- (3)
(3)
÷ 44 stickers + 4 marbles = 19.60
1 sticker + 1 marble = 19.60 ÷ 4
1 sticker + 1 marble = 4.90 --- (4)
(b)
(2) - (4)
(1 sticker + 3 marbles) - (1 sticker + 1 marble) = 12.50 - 4.90
1 sticker - 1 sticker + 3 marbles - 1 marble = 7.60
2 marbles = 7.60
1 marble = 7.60 ÷ 2 = 3.80
Cost of 1 marble = $3.80
(c)
Substitute 1 marble = 3.80 into (4).
1 sticker + 1 marble = 4.90
1 sticker + 3.80 = 4.90
1 sticker = 4.90 - 3.80 = 1.10
Cost of 1 sticker = $1.10
(d)
(4)
x 5 1 sticker + 1 marble = 4.90
5 x (1 sticker + 1 marble) = 5 x 4.90
5 stickers + 5 marbles = 24.50
Cost of 5 stickers and 5 marbles = $24.50
Answer(s): (a) $4.90; (b) $3.80; (c) $1.10; (d) $24.50