Ryan has 2 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 $4.70 more than the total value of 10-cent coins. How many coins did he have in the end?
|
20¢ |
10¢ |
Before |
1 u + 2 |
1 u |
Change |
- 18 |
|
After |
1 u - 16 |
1 u |
|
20¢ |
10¢ |
Number |
1 u - 16 |
1 u |
Value |
20 |
10 |
Total value |
20 u - 320 |
10 u |
$1 = 100¢
$4.70 = 470¢
Number of 20¢ coins in the end
= 1 u + 2 - 18
= 1 u - 16
Total value of 20¢ coins in the end
= 20 x (1 u - 16)
= 20 u - 320
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 470¢ more than the value of 10-cent coins. If another 470¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.
20 u - 320 = 10 u + 470
20 u - 10 u = 470 + 320
10 u = 790
1 u = 790 ÷ 10 = 79
Number of coins that Ryan had in the end
= 1 u + 1 u - 16
= 2 u - 16
= (2 x 79) - 16
= 158 - 16
= 142
Answer(s): 142