5 marbles and 1 sticker cost $16.10.
1 marble and 5 stickers cost $18.10.
- 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 7 marbles and 7 stickers.
(a)
5 marbles + 1 sticker = 16.10 --- (1)
1 marble + 5 stickers = 18.10 --- (2)
(1) + (2)
6 marbles + 6 stickers = 16.10 + 18.10
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) = 18.10 - 5.70
1 marble - 1 marble + 5 stickers - 1 sticker = 12.40
4 stickers = 12.40
1 sticker = 12.40 ÷ 4 = 3.10
Cost of 1 sticker = $3.10
(c)
Substitute 1 sticker = 3.10 into (4).
1 marble + 1 sticker = 5.70
1 marble + 3.10 = 5.70
1 marble = 5.70 - 3.10 = 2.60
Cost of 1 marble = $2.60
(d)
(4)
x 7 1 marble + 1 sticker = 5.70
7 x (1 marble + 1 marble) = 7 x 5.70
7 marbles + 7 stickers = 39.90
Cost of 7 marbles and 7 stickers = $39.90
Answer(s): (a) $5.70; (b) $3.10; (c) $2.60; (d) $39.90