5 marbles and 1 sticker cost $13.90.
1 marble and 5 stickers cost $23.90.
- 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 = 13.90 --- (1)
1 marble + 5 stickers = 23.90 --- (2)
(1) + (2)
6 marbles + 6 stickers = 13.90 + 23.90
6 marbles + 6 stickers = 37.80 --- (3)
(3)
÷ 66 marbles + 6 stickers = 37.80
1 marble + 1 sticker = 37.80 ÷ 6
1 marble + 1 sticker = 6.30 --- (4)
(b)
(2) - (4)
(1 marble + 5 stickers) - (1 marble + 1 marble) = 23.90 - 6.30
1 marble - 1 marble + 5 stickers - 1 sticker = 17.60
4 stickers = 17.60
1 sticker = 17.60 ÷ 4 = 4.40
Cost of 1 sticker = $4.40
(c)
Substitute 1 sticker = 4.40 into (4).
1 marble + 1 sticker = 6.30
1 marble + 4.40 = 6.30
1 marble = 6.30 - 4.40 = 1.90
Cost of 1 marble = $1.90
(d)
(4)
x 6 1 marble + 1 sticker = 6.30
6 x (1 marble + 1 marble) = 6 x 6.30
6 marbles + 6 stickers = 37.80
Cost of 6 marbles and 6 stickers = $37.80
Answer(s): (a) $6.30; (b) $4.40; (c) $1.90; (d) $37.80