2 marbles and 1 sticker cost $9.20.
1 marble and 2 stickers cost $9.70.
- 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)
2 marbles + 1 sticker = 9.20 --- (1)
1 marble + 2 stickers = 9.70 --- (2)
(1) + (2)
3 marbles + 3 stickers = 9.20 + 9.70
3 marbles + 3 stickers = 18.90 --- (3)
(3)
÷ 3
3 marbles + 3 stickers = 18.90
1 marble + 1 sticker = 18.90 ÷ 3
1 marble + 1 sticker = 6.30 --- (4)
Cost of 1 marble and 1 sticker = $6.30
(b)
(2) - (4)
(1 marble + 2 stickers) - (1 marble + 1 marble) = 9.70 - 6.30
1 marble - 1 marble + 2 stickers - 1 sticker = 3.40
1 sticker = 3.40
Cost of 1 sticker = $3.40
(c)
Substitute 1 sticker = 3.40 into (4).
1 marble + 1 sticker = 6.30
1 marble + 3.40 = 6.30
1 marble = 6.30 - 3.40 = 2.90
Cost of 1 marble = $2.90
(d)
(4)
x 9 1 marble + 1 sticker = 6.30
9 x (1 marble + 1 marble) = 9 x 6.30
9 marbles + 9 stickers = 56.70
Cost of 9 marbles and 9 stickers = $56.70
Answer(s): (a) $6.30; (b) $3.40; (c) $2.90; (d) $56.70