Zeph has 4 more 20-cent coins than 10-cent coins. After he used 19 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 in the end?

	20¢	10¢
Before	1 u + 4	1 u
Change	- 19
After	1 u - 15	1 u

	20¢	10¢
Number	1 u - 15	1 u
Value	20	10
Total value	20 u - 300	10 u

$1 = 100¢
$3.80 = 380¢

Number of 20¢ coins in the end
= 1 u + 4 - 19
= 1 u - 15

Total value of 20¢ coins in the end
= 20 x (1 u - 15)
= 20 u - 300

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

After using 19 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 - 300 = 10 u + 380
20 u - 10 u = 380 + 300
10 u = 680

1 u = 680 ÷ 10 = 68

Number of coins that Zeph had in the end
= 1 u + 1 u - 15
= 2 u - 15
= (2 x 68) - 15
= 136 - 15
= 121

Answer(s): 121