Adam spends $12.20 on 3 marbles and 4 stickers.
A marble costs $2.90 more than 1 sticker.
- How much does 1 marble cost?
- How much do 7 marbles cost?
- How much do a sticker and 7 marbles cost?
- How much do 7 marbles cost more than 1 sticker?
(a)
Let the cheaper item be 1 u.
Cost of 1 sticker = 1 u
Cost of 1 marble = 1 u + 2.90
Total cost of 3 marbles and 4 stickers
= 3(1 u + 2.90) + 4 u
= 3 u + 8.70 + 4 u
= 3 u + 4 u + 8.70
= 7 u + 8.70
7 u + 8.70 = 12.20
7 u = 12.20 - 8.70
7 u = 3.50
1 u = 3.50 ÷ 7 = 0.50
Cost of 1 marble
= 1 u + 2.90
= 0.50 + 2.90
= $3.40
(b)
Cost of 7 marbles
= 7 x 3.40
= $23.80
(c)
Cost of 1 sticker and 7 marbles
= 0.50 + 23.80
= $24.30
(d)
Cost of 7 marbles more than 1 sticker
= 23.80 - 0.50
= $23.30
Answer(s): (a) $3.40; (b) $23.80; (c) $24.30; (d) $23.30
