Peter has 8 more 20-cent coins than 5-cent coins. After he used 20 of his 20-cent coins, the total value of 20-cent coins is $3.90 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 |
- 20 |
|
After |
1 u - 12 |
1 u |
|
20¢ |
5¢ |
Number |
1 u - 12 |
1 u |
Value |
20 |
5 |
Total value |
20 u - 240 |
5 u |
$1 = 100¢
$3.90 = 390¢
Number of 20¢ coins in the end
= 1 u + 8 - 20
= 1 u - 12
Total value of 20¢ coins in the end
= 20 x (1 u - 12)
= 20 u - 240
Total value of 5¢ coins in the end
= 5 x 1 u
= 5 u
After using 20 20-cent coins, the value of 20-cent coins is 390¢ more than the value of 5-cent coins. If another 390¢ is added to the 5-cent coins, the total value of 20-cent coins and 5-cent coins will be the same.
20 u - 240 = 5 u + 390
20 u - 5 u = 390 + 240
15 u = 630
1 u = 630 ÷ 15 = 42
Number of coins that Peter had at first
= 1 u + 1 u + 8
= 2 u + 8
= (2 x 42) + 8
= 84 + 8
= 92
Answer(s): 92