The number of five-cent coins in a bottle was
13 the number of twenty-cent coins. Cody took out 15 twenty-cent coins and exchanged them for five-cent coins. Then he put the money back into the bottle. The number of twenty-cent coins became
25 the number of five-cent coins. How much money was there in the bottle?
|
Make u the same (1)x3 = (3) |
5-cent (1) |
20-cent (2) |
Before |
3 u |
1 u |
3 u |
Change |
+ 180 |
+ 60 |
- 15 |
After |
15 p |
5 p |
2 p |
Value of 20-cent coins to be exchanged to 5-cent coins
= 15 x 20
= 300
Number of 5-cent coins to be exchanged from the 20-cent coins
= 300 ÷ 5
= 60
(3) = (2)
15 p - 180 = 2 p + 15
15 p - 2 p = 15 + 180
13 p = 195
1 p = 195 ÷ 13 = 15
Number of 5-cent coins in the end
= 5 p
= 5 p x 15
= 75
Value of 5-cent coins in the end
= 75 x 5
= 375¢
Number of 20-cent coins in the end
= 2 p
= 2 x 15
= 30
Value of 20-cent coins in the end
= 30 x 20
= 600¢
Total value of coins
= 375 + 600
= 975¢
$1 = 100¢
975¢ = $9.75
Answer(s): $9.75