Adam spends $16.70 on 3 marbles and 4 stickers.
A marble costs $2.30 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 + 2.30
Total cost of 3 marbles and 4 stickers
= 3(1 u + 2.30) + 4 u
= 3 u + 6.90 + 4 u
= 3 u + 4 u + 6.90
= 7 u + 6.90
7 u + 6.90 = 16.70
7 u = 16.70 - 6.90
7 u = 9.80
1 u = 9.80 ÷ 7 = 1.40
Cost of 1 marble
= 1 u + 2.30
= 1.40 + 2.30
= $3.70
(b)
Cost of 7 marbles
= 7 x 3.70
= $25.90
(c)
Cost of 1 sticker and 7 marbles
= 1.40 + 25.90
= $27.30
(d)
Cost of 7 marbles more than 1 sticker
= 25.90 - 1.40
= $24.50
Answer(s): (a) $3.70; (b) $25.90; (c) $27.30; (d) $24.50