5 marbles and 1 sticker cost $13.30.
1 marble and 5 stickers cost $20.90.
- Find the cost of 1 marble and 1 sticker.
- Find the cost of 1 sticker.
- Find the cost of 1 marble.
- Find the cost of 6 marbles and 6 stickers.
(a)
5 marbles + 1 sticker = 13.30 --- (1)
1 marble + 5 stickers = 20.90 --- (2)
(1) + (2)
6 marbles + 6 stickers = 13.30 + 20.90
6 marbles + 6 stickers = 34.20 --- (3)
(3)
÷ 66 marbles + 6 stickers = 34.20
1 marble + 1 sticker = 34.20 ÷ 6
1 marble + 1 sticker = 5.70 --- (4)
(b)
(2) - (4)
(1 marble + 5 stickers) - (1 marble + 1 marble) = 20.90 - 5.70
1 marble - 1 marble + 5 stickers - 1 sticker = 15.20
4 stickers = 15.20
1 sticker = 15.20 ÷ 4 = 3.80
Cost of 1 sticker = $3.80
(c)
Substitute 1 sticker = 3.80 into (4).
1 marble + 1 sticker = 5.70
1 marble + 3.80 = 5.70
1 marble = 5.70 - 3.80 = 1.90
Cost of 1 marble = $1.90
(d)
(4)
x 6 1 marble + 1 sticker = 5.70
6 x (1 marble + 1 marble) = 6 x 5.70
6 marbles + 6 stickers = 34.20
Cost of 6 marbles and 6 stickers = $34.20
Answer(s): (a) $5.70; (b) $3.80; (c) $1.90; (d) $34.20