Adam spends $16.40 on 3 marbles and 4 stickers.
A marble costs $2.20 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 + 2.20
Total cost of 3 marbles and 4 stickers
= 3(1 u + 2.20) + 4 u
= 3 u + 6.60 + 4 u
= 3 u + 4 u + 6.60
= 7 u + 6.60
7 u + 6.60 = 16.40
7 u = 16.40 - 6.60
7 u = 9.80
1 u = 9.80 ÷ 7 = 1.40
Cost of 1 marble
= 1 u + 2.20
= 1.40 + 2.20
= $3.60
(b)
Cost of 8 marbles
= 8 x 3.60
= $28.80
(c)
Cost of 1 sticker and 8 marbles
= 1.40 + 28.80
= $30.20
(d)
Cost of 8 marbles more than 1 sticker
= 28.80 - 1.40
= $27.40
Answer(s): (a) $3.60; (b) $28.80; (c) $30.20; (d) $27.40