Find the Last Five Digits....

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Find the Last Five Digits....

by aakgoel » Sun May 27, 2012 11:51 am
PLEASE HELP IN SOLVING THE FOLLOWING PROBLEM....

What would be the five last digits of

(101^100)-1

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by eagleeye » Sun May 27, 2012 1:47 pm
Hi aakgoel:

This is how I did it using pattern recognition.

First, observe the numbers in bold and the underlined:
101^1 = 101
101^2 = 10201
101^3 = 1030301
101^4 = 104060401

We can see that for each successive power of 101, the last two digits remain the same, but the third digit is the same as power. Therefore, for 100,
101^100 = something10001.
Therefore : 101^100 - 1 = something10000
Hence the last 5 digits are 10000

Let me know if that helps :)