Sean has 2 more 20-cent coins than 5-cent coins. After he used 3 of his 20-cent coins, the total value of 20-cent coins is $1.90 more than the total value of 5-cent coins. How many coins did he have at first?
| |
20¢ |
5¢ |
| Before |
1 u + 2 |
1 u |
| Change |
- 3 |
|
| After |
1 u - 1 |
1 u |
| |
20¢ |
5¢ |
| Number |
1 u - 1 |
1 u |
| Value |
20 |
5 |
| Total value |
20 u - 20 |
5 u |
$1 = 100¢
$1.90 = 190¢
Number of 20¢ coins in the end
= 1 u + 2 - 3
= 1 u - 1
Total value of 20¢ coins in the end
= 20 x (1 u - 1)
= 20 u - 20
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 3 20-cent coins, the value of 20-cent coins is 190¢ more than the value of 5-cent coins. If another 190¢ is added to the 5-cent coins, the total value of 20-cent coins and 5-cent coins will be the same.
20 u - 20 = 5 u + 190
20 u - 5 u = 190 + 20
15 u = 210
1 u = 210 ÷ 15 = 14
Number of coins that Sean had at first
= 1 u + 1 u + 2
= 2 u + 2
= (2 x 14) + 2
= 28 + 2
= 30
Answer(s): 30
