Carl has 3 more 20-cent coins than 10-cent coins. After he used 4 of his 20-cent coins, the total value of 20-cent coins is $1.40 more than the total value of 10-cent coins. How many coins did he have at first?
|
20¢ |
10¢ |
Before |
1 u + 3 |
1 u |
Change |
- 4 |
|
After |
1 u - 1 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 1 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 20 |
10 u |
$1 = 100¢
$1.40 = 140¢
Number of 20¢ coins in the end
= 1 u + 3 - 4
= 1 u - 1
Total value of 20¢ coins in the end
= 20 x (1 u - 1)
= 20 u - 20
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 4 20-cent coins, the value of 20-cent coins is 140¢ more than the value of 10-cent coins. If another 140¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 20 = 10 u + 140
20 u - 10 u = 140 + 20
10 u = 160
1 u = 160 ÷ 10 = 16
Number of coins that Carl had at first
= 1 u + 1 u + 3
= 2 u + 3
= (2 x 16) + 3
= 32 + 3
= 35
Answer(s): 35