Adam spends $16.70 on 4 marbles and 5 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 4 marbles and 5 stickers
= 4(1 u + 1.70) + 5 u
= 4 u + 6.80 + 5 u
= 4 u + 5 u + 6.80
= 9 u + 6.80
9 u + 6.80 = 16.70
9 u = 16.70 - 6.80
9 u = 9.90
1 u = 9.90 ÷ 9 = 1.10
Cost of 1 marble
= 1 u + 1.70
= 1.10 + 1.70
= $2.80
(b)
Cost of 7 marbles
= 7 x 2.80
= $19.60
(c)
Cost of 1 sticker and 7 marbles
= 1.10 + 19.60
= $20.70
(d)
Cost of 7 marbles more than 1 sticker
= 19.60 - 1.10
= $18.50
Answer(s): (a) $2.80; (b) $19.60; (c) $20.70; (d) $18.50