Example 3: How many 4 digit numbers that are divisible by 10 can be formed from the numbers 3, 5, 7, 8, 9, 0 such that no number repeats?
Solution: If a number is divisible by 10, its units place should contain a 0.
_ _ _ 0
After 0 is placed in the units place, the tens place can be filled with any of the other 5 digits.
Selecting one digit out of 5 digits can be done in 5C1 = 5 ways.
After filling the tens place, we are left with 4 digits. Selecting 1 digit out of 4 digits can be done in 4C1 = 4 ways.
After filling the hundreds place, the thousands place can be filled in 3C1 = 3 ways.
Therefore, the total combinations possible = 543 = 60
