Paul has 4 more 20-cent coins than 10-cent coins. After he used 6 of his 20-cent coins, the total value of 20-cent coins is $1.30 more than the total value of 10-cent coins. How many coins did he have at first?
|
20¢ |
10¢ |
Before |
1 u + 4 |
1 u |
Change |
- 6 |
|
After |
1 u - 2 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 2 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 40 |
10 u |
$1 = 100¢
$1.30 = 130¢
Number of 20¢ coins in the end
= 1 u + 4 - 6
= 1 u - 2
Total value of 20¢ coins in the end
= 20 x (1 u - 2)
= 20 u - 40
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 6 20-cent coins, the value of 20-cent coins is 130¢ more than the value of 10-cent coins. If another 130¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 40 = 10 u + 130
20 u - 10 u = 130 + 40
10 u = 170
1 u = 170 ÷ 10 = 17
Number of coins that Paul had at first
= 1 u + 1 u + 4
= 2 u + 4
= (2 x 17) + 4
= 34 + 4
= 38
Answer(s): 38