Adam spends $15.60 on 3 marbles and 4 stickers.
A marble costs $1.70 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 + 1.70
Total cost of 3 marbles and 4 stickers
= 3(1 u + 1.70) + 4 u
= 3 u + 5.10 + 4 u
= 3 u + 4 u + 5.10
= 7 u + 5.10
7 u + 5.10 = 15.60
7 u = 15.60 - 5.10
7 u = 10.50
1 u = 10.50 ÷ 7 = 1.50
Cost of 1 marble
= 1 u + 1.70
= 1.50 + 1.70
= $3.20
(b)
Cost of 7 marbles
= 7 x 3.20
= $22.40
(c)
Cost of 1 sticker and 7 marbles
= 1.50 + 22.40
= $23.90
(d)
Cost of 7 marbles more than 1 sticker
= 22.40 - 1.50
= $20.90
Answer(s): (a) $3.20; (b) $22.40; (c) $23.90; (d) $20.90