# Solution 91: The Last Three Digits of a Phi-Exponent Tower

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• Published on May 15, 2019
• For a quick computational overview of Euler's Totient Theorem and Chinese Remainder Theorem: usclip.net/video/vv57_W5HMTg/video.html
Congratulations to Jaleb, Minh Cong Nguyen, Kevin Lu, Serengeti Ghasa, Arghyadeep Chatterjee, Nicolas Nauli, Midas Schonewille, and Mokou Fujiwara for successfully solving this math challenge question! Juju Mas was the first person to solve the question.
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For more Weekly Math Challenges:

• Shakeitpiggy 3 months ago +1

Wow. I did it by finding patterns in the last 2-3 digits of powers of 6 and powers of 8. I still arrived at the right answer though.'

• Jan Von Schreibe 3 months ago

What does it mean that a number _p_ is relatively prime to another number _n_ ?
Is is that _p_ does not divide _n_ ?

• Alberto Zordan 3 months ago +1

No. Two numbers are co-prime (relatively prime to each other) if they do not share any common factors, or equivalently if their greatest common divisor is 1.

• Dragon95161 3 months ago +1

Really great video, how do you come up with these awesome maths questions???

• adandap 3 months ago +1

I was frustratingly close to that. Of your N steps, I had N-2 of them written down but couldn't quite pull it all together. I'll work through it carefully and hopefully the next time Euler raises his head I'll get there.

• KRISHNA KAMALAKANNAN 3 months ago

When are you releasing the solution for this week's video?

• Sitanshu Chaudhary 3 months ago

But how to take mod 1000 by u 1:30

• Zamir C 3 months ago +13

I hope this video helps me to get a GF and stop watching ecchi animes

• The Maverick! 3 months ago +5

@Zain Majumder I did that. No luck.

• Zain Majumder 3 months ago +3

i wish you luck, maybe you'll get girls by demonstrating your mathematical prowess

• The Cold Tomato 3 months ago +2

Will you go over the 2019 FRQ problems for the AP Calculus BC test when it is released?

• LetsSolveMathProblems  3 months ago

@Smokie Bear 🔴🔵 *Edit: After much debate, I decided to not upload AP FRQ videos for this year, mainly because I believe I cannot post a series of explanation that is of a significantly higher quality than those already posted. If you are interested, turksvids has uploaded all solutions to AP Calclus AB/BC FRQ's from this year: usclip.net/user/turksvids

• LetsSolveMathProblems  3 months ago

*Edit: After much debate, I decided to not upload AP FRQ videos for this year, mainly because I believe I cannot post a series of explanation that is of a significantly higher quality than those already posted. If you are interested, turksvids has uploaded all solutions to AP Calclus AB/BC FRQ's from this year: usclip.net/user/turksvids

• The Cold Tomato 3 months ago

@Smokie Bear 🔴🔵 So did I

• Smokie Bear 🔴🔵 3 months ago

I’m so mad. I think I got all the multiple choice right but on ONE part of ONE free response I made ONE mistake cuz I just assumed that the question was asked in the same way as it was in the practice questions. NotLikeThis

• LetsSolveMathProblems  3 months ago +4

I do plan to review AP Calculus AB and BC Free Response problems once they are released. Best of luck on your score if you took the exam today! =)