A probability problem by Kaushik Surai
Probability
Level
pending
A 9 digit palindrome number is formed by using the digits from 1 ,2,3,4,5,6,7,8,9,0 where repetition is allowed. In how many ways the number can be formed.
9*10^4
9^9
10^5
9*10^8
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
For a 9 digit palindrome number first digit and last digit will be same. This is same for second and second last . As there are 9 digits we can only consider the first 5 digits . First digit can not be 0 so there is 9 possibilities for the first digit. Now for the next four digits there are 10 possibilities for each of them. And for the last four digits there are 1 possibility as the number is palindrome.
So total number of ways is = 9 * 10 * 10 * 10 * 10 * 1= 9*10^4