Adam pays $31.40 for 1 marble and 7 stickers.
The marble costs $1.80 more than each sticker.
- What is the cost of 1 marble?
- How much is the cost of 7 marbles and 4 stickers?
(a)
Choose the cheaper item to be 1 u.
Cost of 1 sticker = 1 u
Cost of 1 marble = 1 u + 1.80
Cost of 7 stickers
= 7 x 1 u
= 7 u
Total cost of 1 marble and 7 stickers
= 1 u + 1.80 + 7 u
= 8 u + 1.80
8 u + 1.80 = 31.40
8 u = 31.40 - 1.80
8 u = 29.60
1 u = 29.60 ÷ 8 = 3.70
Cost of 1 marble
= 3.70 + 1.80
= $5.50
(b)
Cost of 7 marbles and 4 stickers
= 7 x 5.50 + 4 x 3.70
= 38.50 + 14.80
= $53.30
Answer(s): (a) $5.50; (b) $53.30