Rael has 4 more 20-cent coins than 10-cent coins. After he used 13 of his 20-cent coins, the total value of 20-cent coins is $2.70 more than the total value of 10-cent coins. How many coins did he have in the end?
|
20¢ |
10¢ |
Before |
1 u + 4 |
1 u |
Change |
- 13 |
|
After |
1 u - 9 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 9 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 180 |
10 u |
$1 = 100¢
$2.70 = 270¢
Number of 20¢ coins in the end
= 1 u + 4 - 13
= 1 u - 9
Total value of 20¢ coins in the end
= 20 x (1 u - 9)
= 20 u - 180
Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u
After using 13 20-cent coins, the value of 20-cent coins is 270¢ more than the value of 10-cent coins. If another 270¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 180 = 10 u + 270
20 u - 10 u = 270 + 180
10 u = 450
1 u = 450 ÷ 10 = 45
Number of coins that Rael had in the end
= 1 u + 1 u - 9
= 2 u - 9
= (2 x 45) - 9
= 90 - 9
= 81
Answer(s): 81