palindrom probability

juantheron · 2012-01-01 02:16:33

Let X be a set of all 13 digit Integers where each digit can take values from 0 to 9 . An Integer is choosen at random from X

. then find the probability that it is a palindrome

John E. Franklin · 2012-01-01 03:53:05

Can the 1st and 13th digit be only 1 to 9, or can they be zeros.
I only like this problem if the 0 is included due to the symmetry of the problem.
But then it might not be an Integer.
Is 0000007000000 a good example of an allowable Integer in this problem?

John E. Franklin · 2012-01-01 05:02:15

Oh, I just thought of the answer.
Pair up the mirrored digits and you get:
10 times 10 times 10 times 10 times 10 times 9 if no zero allowed on end.

John E. Franklin · 2012-01-01 05:04:16

do you see why that works.
See this:
ABCDEFQFEDCBA
The A can be 0 to 9.
The B,C,D,E,F can to 0 to 1 to 9, or ten of them.
Get it? Happy new year. Bonne nouvelle ans!!

anonimnystefy · 2012-01-01 08:08:45

hi John

i have a little problem with what you wrote there.

if those are 13 digit numbers,then A cannot be 0 so it goes from 1 to 9.so it will be:
9*10*10*10*10*10*10=9*(10)^6

Last edited by anonimnystefy (2012-01-01 08:48:16)

bobbym · 2012-01-01 08:16:32

Hi juan and all;

John E. Franklin · 2012-01-01 09:11:28

bobbys right!
I meant 1 to 9 for A.

juantheron · 2012-01-02 20:07:59

thanks bobbym and anonimnystefy and Franklin

and belated happy new year 2012

bobbym · 2012-01-02 20:28:06

Hi juantheron;

You are welcome, glad to help.

Math Is Fun Forum

#1 2012-01-01 02:16:33

palindrom probability

#2 2012-01-01 03:53:05

Re: palindrom probability

#3 2012-01-01 05:02:15

Re: palindrom probability

#4 2012-01-01 05:04:16

Re: palindrom probability

#5 2012-01-01 08:08:45

Re: palindrom probability

#6 2012-01-01 08:16:32

Re: palindrom probability

#7 2012-01-01 09:11:28

Re: palindrom probability

#8 2012-01-02 20:07:59

Re: palindrom probability

#9 2012-01-02 20:28:06

Re: palindrom probability

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