gurpreetsingh
Similar question to test what you have learnt from the previous post.
What is the remainder when \(32^{32^{32}}\) is
divided by 9?
A. 7
B. 4
C. 2
D. 0
E. 1
32^{32^{32}}=(27+5)^{32^{32}}
Solving this binomial power only the last term won't be divisible by 9, so let's consider only this term:
5^{32^{32}}=5^{2^{5*32}}=5^{2^{160}}
Let's consider ciclicity when a power of 5 is divided by 9 (NO WAY I COULD DO THIS ON TEST DAY!!!):
- 5^1 divided by 9 gives a reminder of 5
- 5^2 divided by 9 gives a reminder of 7
- 5^3 divided by 9 gives a reminder of 8
- 5^4 divided by 9 gives a reminder of 4- 5^5 divided by 9 gives a reminder of 2
- 5^6 divided by 9 gives a reminder of 1
- 5^7 divided by 9 gives a reminder of 5
- 5^8 divided by 9 gives a reminder of 7
- 5^9 divided by 9 gives a reminder of 8
- 5^10 divided by 9 gives a reminder of 4
...
Therefore ciclicity is 6.
Let's divide our exponent 2^{160} by 6 and figure out the reminder.
Ciclicty for power of 2 divided by 6 is:
- 2^1 divided by 6 gives a reminder of 2
- 2^2 divided by 6 gives a reminder of 4
- 2^3 divided by 6 gives a reminder of 2
- 2^4 divided by 6 gives a reminder of 4
...
For even exponents the reminder is always
4 (use it to go back in the previous ciclicity and pick the right number).
THE REMINDER IS 4
CORRECT ANS IS B!!