Harry has 8 more 20-cent coins than 10-cent coins. After he used 16 of his 20-cent coins, the total value of 20-cent coins is $2.20 more than the total value of 10-cent coins. How many coins did he have at first?
|
20¢ |
10¢ |
Before |
1 u + 8 |
1 u |
Change |
- 16 |
|
After |
1 u - 8 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 8 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 160 |
10 u |
$1 = 100¢
$2.20 = 220¢
Number of 20¢ coins in the end
= 1 u + 8 - 16
= 1 u - 8
Total value of 20¢ coins in the end
= 20 x (1 u - 8)
= 20 u - 160
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 16 20-cent coins, the value of 20-cent coins is 220¢ more than the value of 10-cent coins. If another 220¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 160 = 10 u + 220
20 u - 10 u = 220 + 160
10 u = 380
1 u = 380 ÷ 10 = 38
Number of coins that Harry had at first
= 1 u + 1 u + 8
= 2 u + 8
= (2 x 38) + 8
= 76 + 8
= 84
Answer(s): 84