Adam spends $12.90 on 4 marbles and 5 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 4 marbles and 5 stickers
= 4(1 u + 1.20) + 5 u
= 4 u + 4.80 + 5 u
= 4 u + 5 u + 4.80
= 9 u + 4.80
9 u + 4.80 = 12.90
9 u = 12.90 - 4.80
9 u = 8.10
1 u = 8.10 ÷ 9 = 0.90
Cost of 1 marble
= 1 u + 1.20
= 0.90 + 1.20
= $2.10
(b)
Cost of 8 marbles
= 8 x 2.10
= $16.80
(c)
Cost of 1 sticker and 8 marbles
= 0.90 + 16.80
= $17.70
(d)
Cost of 8 marbles more than 1 sticker
= 16.80 - 0.90
= $15.90
Answer(s): (a) $2.10; (b) $16.80; (c) $17.70; (d) $15.90