Video Part 1

firstNum is an integer, say 10.

secondNum is also an integer, say 3.

then in Java,

firstNum / secondNum is treated as integer division
with the result 3.  The fraction (remainder) is lost.

To get the remainder use the modulo operator %.

firstNum % secondNum is 1, the remainder of dividing
10 by 3.

Video Part 2

We can exploit this to calculate time in hrs, min, and
sec given total seconds

Given 10000 seconds, find how many hours ,minutes, 
and seconds.

10000 / 3600 (seconds in an hour) is 2 hours using 
(integer division)

The remainder, 10000 % 3600 (read 10000 modulo 3600)
is 2800.  Now we have 10000 sec = 2 hrs plus 2800 sec.

Repeat with the remainder and find out how mant minutes.
2800 / 60 is 46 min and 2800 % 60 is 40.

So 10000 sec is 2 hrs, 46 min, and 40 sec.

You can do the same with money.  Start with
cents instead of seconds, then use integer division
and modulo to work out various denominations of
bills and coins.  For example, to get dollar bills,
divide the cents by 100, and so forth.  

Use the ConvertSeconds program as a model to calculate
money.