Adam spends $14.40 on 3 marbles and 4 stickers.
A marble costs $1.30 more than 1 sticker.
- How much does 1 marble cost?
- How much do 4 marbles cost?
- How much do a sticker and 4 marbles cost?
- How much do 4 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 + 1.30
Total cost of 3 marbles and 4 stickers
= 3(1 u + 1.30) + 4 u
= 3 u + 3.90 + 4 u
= 3 u + 4 u + 3.90
= 7 u + 3.90
7 u + 3.90 = 14.40
7 u = 14.40 - 3.90
7 u = 10.50
1 u = 10.50 ÷ 7 = 1.50
Cost of 1 marble
= 1 u + 1.30
= 1.50 + 1.30
= $2.80
(b)
Cost of 4 marbles
= 4 x 2.80
= $11.20
(c)
Cost of 1 sticker and 4 marbles
= 1.50 + 11.20
= $12.70
(d)
Cost of 4 marbles more than 1 sticker
= 11.20 - 1.50
= $9.70
Answer(s): (a) $2.80; (b) $11.20; (c) $12.70; (d) $9.70