A palindrome number is the same either read from left to right or right to left, for example, 121.121. How many 55digit palindrome numbers are there altogether??


Answer:

900900

Step by Step Explanation:
  1. We need to find the total number of 55 digit palindrome numbers.
  2. 1010 digits (0,1,2,,9)(0,1,2,,9) can be used to fill in the places in the number.
    The first digit cannot be zero in order to make it a 55 digit number.
    Therefore, We have 99 choices for the first place.
    For the 2nd2nd and the 3rd3rd place, we have 1010 choices each.
  3. For a 55digit number to be a palindrome number the 1st1st and the 5th5th , the 2nd2nd and the 4th4th digit of the number needs to be the same.
    Therefore, the total number of 55 digit palindrome numbers =9×10×10=900=9×10×10=900
  4. Hence, there are 900900  5 5digit palindrome numbers altogether.

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