Mark has 4 more 10-cent coins than 5-cent coins. After he used 5 of his 10-cent coins, the total value of 10-cent coins is $2.40 more than the total value of 5-cent coins. How many coins did he have in the end?
|
10¢ |
5¢ |
Before |
1 u + 4 |
1 u |
Change |
- 5 |
|
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¢
$2.40 = 240¢
Number of 10¢ coins in the end
= 1 u + 4 - 5
= 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 5 10-cent coins, the value of 10-cent coins is 240¢ more than the value of 5-cent coins. If another 240¢ 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 + 240
10 u - 5 u = 240 + 10
5 u = 250
1 u = 250 ÷ 5 = 50
Number of coins that Mark had in the end
= 1 u + 1 u - 1
= 2 u - 1
= (2 x 50) - 1
= 100 - 1
= 99
Answer(s): 99