Adam spends $13.40 on 3 marbles and 4 stickers.
A marble costs $1.20 more than 1 sticker.
- How much does 1 marble cost?
- How much do 8 marbles cost?
- How much do a sticker and 8 marbles cost?
- How much do 8 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 = 13.40
7 u = 13.40 - 3.60
7 u = 9.80
1 u = 9.80 ÷ 7 = 1.40
Cost of 1 marble
= 1 u + 1.20
= 1.40 + 1.20
= $2.60
(b)
Cost of 8 marbles
= 8 x 2.60
= $20.80
(c)
Cost of 1 sticker and 8 marbles
= 1.40 + 20.80
= $22.20
(d)
Cost of 8 marbles more than 1 sticker
= 20.80 - 1.40
= $19.40
Answer(s): (a) $2.60; (b) $20.80; (c) $22.20; (d) $19.40
