4 stickers and 1 marble cost $16.60.
1 sticker and 4 marbles cost $19.90.
- 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 5 stickers and 5 marbles.
(a)
4 stickers + 1 marble = 16.60 --- (1)
1 sticker + 4 marbles = 19.90 --- (2)
(1) + (2)
5 stickers + 5 marbles = 16.60 + 19.90
5 stickers + 5 marbles = 36.50 --- (3)
(3)
÷ 55 stickers + 5 marbles = 36.50
1 sticker + 1 marble = 36.50 ÷ 5
1 sticker + 1 marble = 7.30 --- (4)
(b)
(2) - (4)
(1 sticker + 4 marbles) - (1 sticker + 1 marble) = 19.90 - 7.30
1 sticker - 1 sticker + 4 marbles - 1 marble = 12.60
3 marbles = 12.60
1 marble = 12.60 ÷ 3 = 4.20
Cost of 1 marble = $4.20
(c)
Substitute 1 marble = 4.20 into (4).
1 sticker + 1 marble = 7.30
1 sticker + 4.20 = 7.30
1 sticker = 7.30 - 4.20 = 3.10
Cost of 1 sticker = $3.10
(d)
(4)
x 5 1 sticker + 1 marble = 7.30
5 x (1 sticker + 1 marble) = 5 x 7.30
5 stickers + 5 marbles = 36.50
Cost of 5 stickers and 5 marbles = $36.50
Answer(s): (a) $7.30; (b) $4.20; (c) $3.10; (d) $36.50