Adam pays $20.70 for 1 marble and 8 stickers.
The marble costs $1.80 more than each sticker.
- What is the cost of 1 marble?
- How much is the cost of 8 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 8 stickers
= 8 x 1 u
= 8 u
Total cost of 1 marble and 8 stickers
= 1 u + 1.80 + 8 u
= 9 u + 1.80
9 u + 1.80 = 20.70
9 u = 20.70 - 1.80
9 u = 18.90
1 u = 18.90 ÷ 9 = 2.10
Cost of 1 marble
= 2.10 + 1.80
= $3.90
(b)
Cost of 8 marbles and 4 stickers
= 8 x 3.90 + 4 x 2.10
= 31.20 + 8.40
= $39.60
Answer(s): (a) $3.90; (b) $39.60