Sean has 8 more 20-cent coins than 5-cent coins. After he used 10 of his 20-cent coins, the total value of 20-cent coins is $4.70 more than the total value of 5-cent coins. How many coins did he have at first?
|
20¢ |
5¢ |
Before |
1 u + 8 |
1 u |
Change |
- 10 |
|
After |
1 u - 2 |
1 u |
|
20¢ |
5¢ |
Number |
1 u - 2 |
1 u |
Value |
20 |
5 |
Total value |
20 u - 40 |
5 u |
$1 = 100¢
$4.70 = 470¢
Number of 20¢ coins in the end
= 1 u + 8 - 10
= 1 u - 2
Total value of 20¢ coins in the end
= 20 x (1 u - 2)
= 20 u - 40
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 10 20-cent coins, the value of 20-cent coins is 470¢ more than the value of 5-cent coins. If another 470¢ is added to the 5-cent coins, the total value of 20-cent coins and 5-cent coins will be the same.
20 u - 40 = 5 u + 470
20 u - 5 u = 470 + 40
15 u = 510
1 u = 510 ÷ 15 = 34
Number of coins that Sean had at first
= 1 u + 1 u + 8
= 2 u + 8
= (2 x 34) + 8
= 68 + 8
= 76
Answer(s): 76