Adam spends $13.20 on 3 stickers and 4 marbles.
A sticker costs $1.60 more than 1 marble.
- How much does 1 sticker cost?
- How much do 7 stickers cost?
- How much do a marble and 7 stickers cost?
- How much do 7 stickers cost more than 1 marble?
(a)
Let the cheaper item be 1 u.
Cost of 1 marble = 1 u
Cost of 1 sticker = 1 u + 1.60
Total cost of 3 stickers and 4 marbles
= 3(1 u + 1.60) + 4 u
= 3 u + 4.80 + 4 u
= 3 u + 4 u + 4.80
= 7 u + 4.80
7 u + 4.80 = 13.20
7 u = 13.20 - 4.80
7 u = 8.40
1 u = 8.40 ÷ 7 = 1.20
Cost of 1 sticker
= 1 u + 1.60
= 1.20 + 1.60
= $2.80
(b)
Cost of 7 stickers
= 7 x 2.80
= $19.60
(c)
Cost of 1 marble and 7 stickers
= 1.20 + 19.60
= $20.80
(d)
Cost of 7 stickers more than 1 marble
= 19.60 - 1.20
= $18.40
Answer(s): (a) $2.80; (b) $19.60; (c) $20.80; (d) $18.40