Archie has 6 more 10-cent coins than 5-cent coins. After he used 7 of his 10-cent coins, the total value of 10-cent coins is $1.40 more than the total value of 5-cent coins. How many coins did he have at first?
|
10¢ |
5¢ |
Before |
1 u + 6 |
1 u |
Change |
- 7 |
|
After |
1 u - 1 |
1 u |
|
10¢ |
5¢ |
Number |
1 u - 1 |
1 u |
Value |
10 |
5 |
Total value |
10 u - 10 |
5 u |
$1 = 100¢
$1.40 = 140¢
Number of 10¢ coins in the end
= 1 u + 6 - 7
= 1 u - 1
Total value of 10¢ coins in the end
= 10 x (1 u - 1)
= 10 u - 10
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 7 10-cent coins, the value of 10-cent coins is 140¢ more than the value of 5-cent coins. If another 140¢ is added to the 5-cent coins, the total value of 10-cent coins and 5-cent coins will be the same.
10 u - 10 = 5 u + 140
10 u - 5 u = 140 + 10
5 u = 150
1 u = 150 ÷ 5 = 30
Number of coins that Archie had at first
= 1 u + 1 u + 6
= 2 u + 6
= (2 x 30) + 6
= 60 + 6
= 66
Answer(s): 66