Flynn has 4 more 20-cent coins than 10-cent coins. After he used 17 of his 20-cent coins, the total value of 20-cent coins is $3.80 more than the total value of 10-cent coins. How many coins did he have at first?

	20¢	10¢
Before	1 u + 4	1 u
Change	- 17
After	1 u - 13	1 u

	20¢	10¢
Number	1 u - 13	1 u
Value	20	10
Total value	20 u - 260	10 u

$1 = 100¢
$3.80 = 380¢

Number of 20¢ coins in the end
= 1 u + 4 - 17
= 1 u - 13

Total value of 20¢ coins in the end
= 20 x (1 u - 13)
= 20 u - 260

Total value of 10¢ coins in the end
= 10 x 1 u
= 10 u

After using 17 20-cent coins, the value of 20-cent coins is 380¢ more than the value of 10-cent coins. If another 380¢ is added to the 10-cent coins, the total value of 20-cent coins and 10-cent coins will be the same.

20 u - 260 = 10 u + 380
20 u - 10 u = 380 + 260
10 u = 640

1 u = 640 ÷ 10 = 64

Number of coins that Flynn had at first
= 1 u + 1 u + 4
= 2 u + 4
= (2 x 64) + 4
= 128 + 4
= 132

Answer(s): 132