Adam spends $15.50 on 3 marbles and 4 stickers.
A marble costs $1.20 more than 1 sticker.
- How much does 1 marble cost?
- How much do 6 marbles cost?
- How much do a sticker and 6 marbles cost?
- How much do 6 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 + 1.20
Total cost of 3 marbles and 4 stickers
= 3(1 u + 1.20) + 4 u
= 3 u + 3.60 + 4 u
= 3 u + 4 u + 3.60
= 7 u + 3.60
7 u + 3.60 = 15.50
7 u = 15.50 - 3.60
7 u = 11.90
1 u = 11.90 ÷ 7 = 1.70
Cost of 1 marble
= 1 u + 1.20
= 1.70 + 1.20
= $2.90
(b)
Cost of 6 marbles
= 6 x 2.90
= $17.40
(c)
Cost of 1 sticker and 6 marbles
= 1.70 + 17.40
= $19.10
(d)
Cost of 6 marbles more than 1 sticker
= 17.40 - 1.70
= $15.70
Answer(s): (a) $2.90; (b) $17.40; (c) $19.10; (d) $15.70