Harry has 6 more 20-cent coins than 10-cent coins. After he used 18 of his 20-cent coins, the total value of 20-cent coins is $2.90 more than the total value of 10-cent coins. How many coins did he have in the end?
|
20¢ |
10¢ |
Before |
1 u + 6 |
1 u |
Change |
- 18 |
|
After |
1 u - 12 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 12 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 240 |
10 u |
$1 = 100¢
$2.90 = 290¢
Number of 20¢ coins in the end
= 1 u + 6 - 18
= 1 u - 12
Total value of 20¢ coins in the end
= 20 x (1 u - 12)
= 20 u - 240
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 18 20-cent coins, the value of 20-cent coins is 290¢ more than the value of 10-cent coins. If another 290¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 240 = 10 u + 290
20 u - 10 u = 290 + 240
10 u = 530
1 u = 530 ÷ 10 = 53
Number of coins that Harry had in the end
= 1 u + 1 u - 12
= 2 u - 12
= (2 x 53) - 12
= 106 - 12
= 94
Answer(s): 94