Fred has 3 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 $1.40 more than the total value of 10-cent coins. How many coins did he have in the end?
| |
20¢ |
10¢ |
| Before |
1 u + 3 |
1 u |
| Change |
- 6 |
|
| After |
1 u - 3 |
1 u |
| |
20¢ |
10¢ |
| Number |
1 u - 3 |
1 u |
| Value |
20 |
10 |
| Total value |
20 u - 60 |
10 u |
$1 = 100¢
$1.40 = 140¢
Number of 20¢ coins in the end
= 1 u + 3 - 6
= 1 u - 3
Total value of 20¢ coins in the end
= 20 x (1 u - 3)
= 20 u - 60
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 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 - 60 = 10 u + 140
20 u - 10 u = 140 + 60
10 u = 200
1 u = 200 ÷ 10 = 20
Number of coins that Fred had in the end
= 1 u + 1 u - 3
= 2 u - 3
= (2 x 20) - 3
= 40 - 3
= 37
Answer(s): 37
