Permutations with Case Restrictions

09/08/15

In today's class we continued our lesson on permutations. Our main focus in this lesson of permutations was on equations involving only numbers. We were also introduced to equations with not only one but several limitations.

Example:
Using the numbers 2, 4, 5. 6 and 8, how many four digit numbers can be formed if the number is to be less than 5000 and divisible by 5?

2 x 5 x 5 x 1 = 50      or      1 x 5 x 5 x 1 = 25
2 = 5,4                                 1 x 5 x 5 x 1 = 25
1 = 5                                    25 + 25 = 50

The answer is 50 four digit numbers divisible by 5 and less than 5000 can be formed.