Carl has 7 more 20-cent coins than 10-cent coins. After he used 20 of his 20-cent coins, the total value of 20-cent coins is $2.20 more than the total value of 10-cent coins. How many coins did he have in the end?
|
20¢ |
10¢ |
Before |
1 u + 7 |
1 u |
Change |
- 20 |
|
After |
1 u - 13 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 13 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 260 |
10 u |
$1 = 100¢
$2.20 = 220¢
Number of 20¢ coins in the end
= 1 u + 7 - 20
= 1 u - 13
Total value of 20¢ coins in the end
= 20 x (1 u - 13)
= 20 u - 260
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 20 20-cent coins, the value of 20-cent coins is 220¢ more than the value of 10-cent coins. If another 220¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 260 = 10 u + 220
20 u - 10 u = 220 + 260
10 u = 480
1 u = 480 ÷ 10 = 48
Number of coins that Carl had in the end
= 1 u + 1 u - 13
= 2 u - 13
= (2 x 48) - 13
= 96 - 13
= 83
Answer(s): 83