problem on Permutation Combination

Topic: Permutation Combination

what is Permutation : Permutation means arrangement of things. The word arrangement is used, if the order of things is considered.

what is Combination: Combination means selection of things. The word selection is used, when the order of things has no importance.
Here is a simple question on how to find permutation and combination.
Question:-

Find the 5 digit numbers with distinct digits

Solution:-

10 digits are there in total

0,1,2,3,4,5,6,7,8,9

To make 5 digit numbers ,we have to pick 5 different digits such that 1 st one not 0

So ,1 st digit has 9 options

2 nd has 8 options (including 0)
3 rd has 8 options(leaving out the 1 st and 2 nd)

4 th has 7 options (leaving out 1 st 2nd and 3 rd)

5 th has 6 options (leaving out 1 st 2 nd 3 rd and 4 th)

So ,the total number =9*9*8*7*6

=27216

27216 is the answer.


For more help ,please reply me.