Paul has 4 more 10-cent coins than 5-cent coins. After he used 7 of his 10-cent coins, the total value of 10-cent coins is $3.60 more than the total value of 5-cent coins. How many coins did he have in the end?
| |
10¢ |
5¢ |
| Before |
1 u + 4 |
1 u |
| Change |
- 7 |
|
| After |
1 u - 3 |
1 u |
| |
10¢ |
5¢ |
| Number |
1 u - 3 |
1 u |
| Value |
10 |
5 |
| Total value |
10 u - 30 |
5 u |
$1 = 100¢
$3.60 = 360¢
Number of 10¢ coins in the end
= 1 u + 4 - 7
= 1 u - 3
Total value of 10¢ coins in the end
= 10 x (1 u - 3)
= 10 u - 30
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 7 10-cent coins, the value of 10-cent coins is 360¢ more than the value of 5-cent coins. If another 360¢ is added to the 5-cent coins, the total value of 10-cent coins and 5-cent coins will be the same.
10 u - 30 = 5 u + 360
10 u - 5 u = 360 + 30
5 u = 390
1 u = 390 ÷ 5 = 78
Number of coins that Paul had in the end
= 1 u + 1 u - 3
= 2 u - 3
= (2 x 78) - 3
= 156 - 3
= 153
Answer(s): 153
