public boolean isOddNumber(int n)

Given a number (int), return true if the number is odd, false if even.

  boolean odd = false; // default
  if (n % 2 != 0) {
    odd = true;
  }
  return odd;

This next section of problems use the MOD or REMAINDER operation,
which uses the percent sign %.
There are actually TWO answers when you divide one number (a dividend) 
by another (a divisor): a QUOTIENT and a REMAINDER.
For example: 52 divided by 10 gives 5 with a remainder of 2.
In Java, we have TWO different operations for INTEGERS (not floats or doubles): 
    QUOTIENT division, which uses a FORWARD SLASH (/), and
    REMAINDER division, which used the PERCENT SIGN (%).
Therefore:
    52 / 10 gives 5 (the QUOTIENT)
    52 % 10 give 2 (the REMAINDER)

The REMAINDER operation has many uses.

1. You can test for an EVEN number by checking that 
the remainder is 0 when you divide by 2, e.g.  8 % 2 == 0.
Therefore, given a number n, if (n % 2 == 0), then the number is even.

2. You can test for an ODD number by checking that the 
remainder is NOT 0 when you divide by 2, e.g.  7 % 2 != 0
Therefore, given a number n, if (n % 2 != 0), then the number is odd.
This works when n is a NEGATIVE number as well.

NOTE: If n is a POSITIVE number, n % 2 == 1.
HOWEVER: If n is a NEGATIVE number, n % 2 == -1, i.e. the REMAINDER will be -1.
THEREFORE using (n % 2 == 1) to test for an ODD number will not work
when n is NEGATIVE!

3. You can also test whether one number is a factor of the other.
If you divide a number by a DIVISOR and the remainder is zero,
then the divisor is a FACTOR of that number.
Therefore, if n % 6 == 0, then 6 is a FACTOR of n,
and n is a MULTIPLE of 6.
Conversely if n % 6 != 0, then 6 is NOT a FACTOR of n,
and n is NOT a MULTIPLE of 6.

4. Given ANY integer, you can extract the rightmost digit 
(the digit in the 1's column) using MOD 10.
For example:
 7186 % 10 gives 6
  593 % 10 gives 3
   14 % 10 gives 4
    8 % 10 gives 8, etc.

5. Given any integer, you can extract the 2nd-to-rightmost digit 
(the digit in the 10's column) as follows:
 (7186 / 10) % 10 give 8
  (593 / 10) % 10 gives 9
   (25 / 10) % 10 gives 2
    (8 / 10) % 10 gives 0

6. Given any integer, you can extract the digit in the 100's columns 
as follows:
 (7186 / 100) % 10 give 1
  (593 / 100) % 10 gives 5
   (25 / 100) % 10 gives 0
    (8 / 100) % 10 gives 0