Adam spends $14.70 on 2 marbles and 3 stickers.
A marble costs $2.10 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 + 2.10
Total cost of 2 marbles and 3 stickers
= 2(1 u + 2.10) + 3 u
= 2 u + 4.20 + 3 u
= 2 u + 3 u + 4.20
= 5 u + 4.20
5 u + 4.20 = 14.70
5 u = 14.70 - 4.20
5 u = 10.50
1 u = 10.50 ÷ 5 = 2.10
Cost of 1 marble
= 1 u + 2.10
= 2.10 + 2.10
= $4.20
(b)
Cost of 7 marbles
= 7 x 4.20
= $29.40
(c)
Cost of 1 sticker and 7 marbles
= 2.10 + 29.40
= $31.50
(d)
Cost of 7 marbles more than 1 sticker
= 29.40 - 2.10
= $27.30
Answer(s): (a) $4.20; (b) $29.40; (c) $31.50; (d) $27.30