5 marbles and 1 sticker cost $17.90.
1 marble and 5 stickers cost $22.30.
- 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 9 marbles and 9 stickers.
(a)
5 marbles + 1 sticker = 17.90 --- (1)
1 marble + 5 stickers = 22.30 --- (2)
(1) + (2)
6 marbles + 6 stickers = 17.90 + 22.30
6 marbles + 6 stickers = 40.20 --- (3)
(3)
÷ 66 marbles + 6 stickers = 40.20
1 marble + 1 sticker = 40.20 ÷ 6
1 marble + 1 sticker = 6.70 --- (4)
(b)
(2) - (4)
(1 marble + 5 stickers) - (1 marble + 1 marble) = 22.30 - 6.70
1 marble - 1 marble + 5 stickers - 1 sticker = 15.60
4 stickers = 15.60
1 sticker = 15.60 ÷ 4 = 3.90
Cost of 1 sticker = $3.90
(c)
Substitute 1 sticker = 3.90 into (4).
1 marble + 1 sticker = 6.70
1 marble + 3.90 = 6.70
1 marble = 6.70 - 3.90 = 2.80
Cost of 1 marble = $2.80
(d)
(4)
x 9 1 marble + 1 sticker = 6.70
9 x (1 marble + 1 marble) = 9 x 6.70
9 marbles + 9 stickers = 60.30
Cost of 9 marbles and 9 stickers = $60.30
Answer(s): (a) $6.70; (b) $3.90; (c) $2.80; (d) $60.30