Last digit problem

how to solve this please give a solution for it i have found it on internet ${ 7 }^{ { 7 }^{ { 7 }^{ 7... } } }(2008\quad 7's)mod(13)$ and also its last digit

#NumberTheory #Olympiad #AIME

Easy Math Editor

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Comments

hey @Finn Hulse @Sharky Kesa @Krishna Ar or anyone please answer it !!

Rishabh Jain - 6 years, 10 months ago

Whoa! Thanks for tagging me here @Rishabh Jain . Well the answer is that the expression is 6 mod 13 and also 3 mod 10 (last digit). Tell me if its right, if yes, I shall very soon post a full solution. I can perhaps give a small hint that you must analyse the remainders obtained on divison of powers of 7 by 13 till u get a pattern/chain. Or plug in euler :p