Lee has 8 more 10-cent coins than 5-cent coins. After he used 13 of his 10-cent coins, the total value of 10-cent coins is $3.30 more than the total value of 5-cent coins. How many coins did he have at first?
| |
10¢ |
5¢ |
| Before |
1 u + 8 |
1 u |
| Change |
- 13 |
|
| After |
1 u - 5 |
1 u |
| |
10¢ |
5¢ |
| Number |
1 u - 5 |
1 u |
| Value |
10 |
5 |
| Total value |
10 u - 50 |
5 u |
$1 = 100¢
$3.30 = 330¢
Number of 10¢ coins in the end
= 1 u + 8 - 13
= 1 u - 5
Total value of 10¢ coins in the end
= 10 x (1 u - 5)
= 10 u - 50
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 13 10-cent coins, the value of 10-cent coins is 330¢ more than the value of 5-cent coins. If another 330¢ is added to the 5-cent coins, the total value of 10-cent coins and 5-cent coins will be the same.
10 u - 50 = 5 u + 330
10 u - 5 u = 330 + 50
5 u = 380
1 u = 380 ÷ 5 = 76
Number of coins that Lee had at first
= 1 u + 1 u + 8
= 2 u + 8
= (2 x 76) + 8
= 152 + 8
= 160
Answer(s): 160
