To the power of what?

Algebra Level 1

2 2 2 2 0 = ? \LARGE 2^{2^{2^{2^0}}} = \ ?

0 1 16 None of the above

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24 solutions

Louis W
Sep 22, 2015

Many of you are reading this problem as such: ( ( ( 2 2 ) 2 ) 2 ) 0 (((2^{2})^{2})^{2})^{0} If this were what the problem looked like, then you would be right to use the property of exponents that says ( x a ) b = x a b (x^{a})^{b}=x^{ab} and say this simplifies to 2 0 = 1 2^{0}=1 . But that would be wrong, because you see no parenthesis in the original problem. If you see no parenthesis in a problem like this, then you should assume it looks something more like this: 2 ( 2 ( 2 ( 2 0 ) ) ) \Huge{2^{(2^{(2^{(2^{0})})})}} In this case you would simply use the order of operations and work from the inner to outer parenthesis, and that simplifies to 2 4 = 16 2^{4}=\color{#D61F06}{16}\space\space\space\Box

To read more, see: how are exponent towers evaluated?

This solution is on point and 100% correct.

William Adams - 5 years, 8 months ago

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2)0 2) 2) 2

prahlad kumhar - 5 years, 1 month ago

Agreed, though I jumped ahead and didn't think it through. You always work from the inner brackets outward. So 2^(2^(2^(2^(0)))) = 2^(2^(2^(1))) = 2^(2^(2)) = 2^(4) = 16. This was a great little pop brain teaser. I don't use this from the day to day so it's nice to keep fresh.

Andrew Cours - 5 years, 7 months ago

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I forgot about that and went from the top to the bottom

Kalvin Lawson - 5 years, 5 months ago

ohhhhhhhhhhhhhhhhhhhhhhhhhh

Joe Lach - 5 years, 4 months ago

It was a little tricky sorry because I dont see those lasta parentheses either.

Caridad María Alvarez Cardona - 4 years, 8 months ago

That's false in so many levels... you start from the bottoms to the top, same without parentheses. I don't know who wrote those lessons in the app but it's not how math works !

damien G - 5 years, 2 months ago

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@damien G : Actually, you always evaluate power towers from the top down. If you started from the bottom and went up, there would be no reason to add new notation because it can always be expressed more simply.

I recommend looking at 3Blue1Brown's high school lecture on power towers and tetration. Search it up on YouTube.

Ved Pradhan - 11 months, 1 week ago

Thank you!

Dilara Merve - 5 years, 1 month ago

Whether exponentiation is left or right associative is a notational convention, with no structural implications. Left association makes more sense, as it provides a complete construct at each stage of reading. Thus division and subtraction are left associative. Right associativity for exponentiation is a regrettable anomaly that I will just have to accept.

Colin Hastie - 4 years, 3 months ago

Brilliant you are a good teacher🌍🌏🌎🌐🌐🚦🚧🚧💐💐🎤💐💌🎤

Rathindra Neogi - 1 year, 8 months ago

Anything to the zero power is either zero or one (I forgot which it is..been too long since math class :) ). The top most exponent is zero, the others are mere confusion.

Dave Crim - 4 years, 10 months ago

When solving towers of exponents, simply do from the top.

2 2 2 2 0 = 2 2 2 1 = 2 4 = 16 \Large 2^{2^{2^{2^{0}}}} = 2^{2^{2^{1}}}=2^{4}= \boxed{16}

for me 2²=4; 4²=16; 16²=256; 256(0)=1

Jean Pierre Meynard - 5 years, 7 months ago

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That's because you are approaching it incorrectly. Reread the post you are replying to.

Paul Alberti-Strait - 5 years, 6 months ago
John Aries Sarza
May 24, 2014

2 2 2 2 0 = 2 2 2 1 = 2 2 2 = 2 4 = 16 \Large { 2 }^{ { 2 }^{ { 2 }^{ { 2 }^{ 0 } } } }={ 2 }^{ { 2 }^{ { 2 }^{ { 1 } } } }={ 2 }^{ { 2 }^{ { 2 } } }={ 2 }^{ 4 }=16

I think it should be 1 due to power of power is equal to the multiply of the powers like ((X^2)^3)=X^6 and so on !!!!!!!!!!!!!!!!!!!!!!!!!!!!

Laith Hameed - 6 years, 11 months ago

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when evaluating tetration expressed as an "exponentiation tower", the exponentiation is done at the deepest level first (in the notation, at the highest level). In other words:

2^2^2^2^0 = 16 Note that exponentiation is not associative, so evaluating the expression in the other order will lead to a different answer: 2^2^2^2^0 is not equal to {[(2^2)^2]^2}^0 which is 2^(2x2x2x0) = 1

Danrey Vallejos - 5 years, 9 months ago

That exponent law does not apply to this kind of power. Think of it as 3^(3^3) = 3 3 3 = 3 27 3^{3^{3}} = 3^{27} which isn't the same as 3 9 3^{9}

Nicolas Bryenton - 6 years, 10 months ago

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Is anyone missing the 0 on top

Kene Ezechukwu - 5 years, 10 months ago

It should be 1. We first expand inner braket n than outer.

vikas parmar - 5 years, 10 months ago

((X^2)^3)=X^6 and X^2^3 = X^8, this is the reason why you need the "()"

Woody Superman - 5 years, 10 months ago

When handling power towers, you always handle the deepest layer first—same as if there were nested parentheses. The deepest layer being the 2 0 2^{0} at the very top. This should be obvious.

William Bodine - 5 years, 2 months ago

Yes exactly 1

Kene Ezechukwu - 5 years, 10 months ago

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x a b ( x a ) b x^{a^b}\neq (x^{a})^b

Abdur Rehman Zahid - 5 years, 9 months ago

I agree with you..... any number brought to a zero power is equal to one....

John Lyndon - 5 years ago

I agree with u (Y)

Ali Ashraf - 5 years, 9 months ago

I also agree

Umar Baba - 5 years, 9 months ago

Sir . Why can't we start at the bottom .. There's no parentheses that tells us where to start ! Please Give me more sites that states the rules on exponent .. Thanks

Jhoemar Mendiogarin - 5 years, 8 months ago

good question

Aditya Gaur - 6 years, 11 months ago

ok i got it...

Sahar Deni - 5 years, 10 months ago

Don't u think that like this a^0 will be 1 but a^0^2 is 0 Please correct me if Iam wrong please

Sumit Gaur - 5 years, 10 months ago

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Anything raised to zero is one except 0 itself

Zaccaria Joshua Quadros - 5 years, 9 months ago

no. 0^2 is 0 then a^0 is 1.

Andrew Richard Thapa - 5 years, 9 months ago

For those who are not convinced, just Google 2^2^2^2^0

Answer: 16.

By convention, exponentiation towers are evaluated by calculating at the highest (deepest) level first. That is, 2^2^2^2^0 = 2^2^2^(2^0) = 2^2^2^1 = 2^2^(2^1) = 2^2^2 = 2^(2^2) = 2^4 = 16.

Julio Peixoto Schwab - 4 years, 1 month ago

I think that the problem is fundamentally ambiguous, as stated. Matlab gives the solution:

> 2^2^2^2^0

ans = 1

>

which disagrees with the canonical solution that is being presented. I think that is is fair to say that the problem, as stated, is ambiguous, and that the result is implementation dependent.

Andrew Allison - 4 years, 9 months ago

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On paper, superindex exponentation is right-associative. But the (^) operator in computer languages is left associative.

Orlando Moreno - 3 years, 7 months ago

I believe that the order of operations in exponent towers does not default the same way if left vague like this. Where is it cited that power towers must be evaluated top down by default?

I am in the United States, problem writer is in India -- the defaults for notation may not be the same.

Jonathan Nielsen - 5 years, 9 months ago

2^2^2^2^0=2^2^2^0=2^2^0=2^0=1

محمد الجندى - 5 years, 9 months ago

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الحل يبدأ من أعلي والناتج 16

محمد كذلك - 5 years, 9 months ago

it should be 1 because anything to the power of 0= 1

Amber Rose Williams - 5 years, 8 months ago

its 1. suppose we have 2^6 which is equivalent to (2^2)^3 just like the current situation (((2^2)^2)^2)^0 so it evaluates to 2^0 which is 1.

Aamir Munir - 5 years, 8 months ago

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Mr. Aamir, I would like to clarify you that you are misled by your own concept. 2^6 is not equal to 2^2^3, it is 2^2*3 (which is 64 when simplified); not equivalent also to (2^2)^3 because its equivalent is 4^3 or 48. Therefore, with all due respect, your idea is wrong.

Danrey Vallejos - 5 years, 8 months ago

2*0 does not equal 1

William Graf - 5 years, 8 months ago

Wtf.. Based on the rule, you have to multiply exponents with exponents.. so, how can you say that that the answer is 1 if you raise the 2 exponent to 0, because 2 is also a exponent..so you will multiply it to 0.. of course the answer is 0.. then do it so on.. for the last step, the answer will become 2^0 then the answer is 1..Addition.. you can only raise a exponent when you have already the base.. :)

Joshua Frederich Mortel - 5 years, 9 months ago

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i agree with you

Wiljohn Mata - 5 years, 9 months ago

use the rules of exponents to simplify the expression. ( 16² )º, for any rational number a except 0, aº = 1: (16)º raise 16 to the power 0: Output :1

John Ramos - 5 years, 8 months ago

The rules of indices state ( a m ) n = a ( m n ) (a^m)^n = a^{(m*n)} Your expression simplifies to 2 ( 2 2 2 0 ) 2^{(2*2*2*0)} or 2 0 2^0 which equals 1

Mark McCrone - 5 years, 8 months ago

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This problem isn't like (a^m)^n. You are right that that would be equal to a^(m*n). This problem, instead, is like a^(m^n), which is going to be very different unless m and n equal 1 or 2.

Paul Alberti-Strait - 5 years, 6 months ago

i thing it's false

Abdou Mtec - 6 years, 12 months ago

I'm sorry, but you are so wrong. You must multiply the powers, witch will lead to 0. So, 2^0 = 1. How come "brilliant" is considering 16 the correct answer?? Am I missing something here??

Fábio Casado - 5 years, 9 months ago

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If it was [[(2^2)^2]^2]^0 then it will be(16^2)^0 = 1, since there's no brackets you start from the top and the answer is 2^4 which is 16 :[2^(2^2)]^(2^0)

Andrew Richard Thapa - 5 years, 9 months ago

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You cannot raise the exponent with the exponent.. you should multiply it because it's the rule..

Joshua Frederich Mortel - 5 years, 9 months ago

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@Joshua Frederich Mortel In a problem like this, you do raise the exponent with the exponent. If it were ((((2^2)^2)^2)^0) you would be right, but that is not what was written. Without the parentheses it is a tetratrion problem. See here: https://en.m.wikipedia.org/wiki/Tetration

Eleonora Witzky - 5 years, 7 months ago

yeah.. you're right man.. I'm with you.. they're raising the exponent 2 to exponent 0.. its wrong because you have to multiply all exponents until you get the base with the exponent.. then there's the time you can raise the base by the exponent.. 2^(2(2(2x0) instead of 2^(2^(2^(2^0)

Joshua Frederich Mortel - 5 years, 9 months ago

I also answered 1 on the basis that anything to the power of 0 is 1

Gillian Edwards - 5 years, 8 months ago

i think it should be 1 the reason is first we take 2 exponent 2 then again repeat and again repeat once more and finally take exponent 0 and hence answer is 1

Moiz Husnain - 5 years, 9 months ago

It should be 1

Hassan Raza - 5 years, 8 months ago

16 is wrong. The answer is 1. Because it's 2^(2 2 2 2 0) which is 2^(0).

Muhammad Khattab - 5 years, 8 months ago

Nice one but i think 2 by exponent 0 is 0 because of 2x0 is 0 so 2 exp.2 exp.2 exp.2 exp.2 exp. 0 to 2 exp.2 exp.2 exp.0 to 2 exp.2 exp.0 to 2 exponent 0 to 0 so 0

Krishna Mandal - 5 years, 10 months ago

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P.S. Exponent is multiplication so 10^1 is 10 10^0 is 1 and 2^0 is 0 but why is 10^0 1 and 2^0 0 ? Because 1 by 10 is 10 , and so to see 10 times 1 because 10 is a common multiple of 10 by 10 and infinity but two is not because at view , there is no 1 composite with 0 ;which is the number of infinity ; by it . so the answer is 0.

Krishna Mandal - 5 years, 10 months ago

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2^0 is never 0. any number you raise to 0 will always be 1 except 0^0, which is undefined.

Andrew Richard Thapa - 5 years, 9 months ago

Brilliant really needs some quality control. This is wrong. Proof Let x = 2^2^2^0 Then, ln(x) = 2 2 0*ln(2) = 0 Therefore, x = 1

David Doyle - 5 years, 8 months ago

Top to bottom approach is wrong... if you are going from top to bottom, power is equivalent to multiplication, But it will work if you go from bottom to top. Please refer the example below. Question: 3^3^3=? If you go top down as you did as above, it should be 3^27, which turns out to be 7.6256E+12,,,Its something weird. But it should be 3^(3*3)=3^9=19683

Instead you can go from bottom to top,then 3^3^3=(3^3)^3=27^3=19683

So either follow bottom to top approach or do the powers by multiplication if you come top to bottom.

So the correct answer should be 1, not 16

Geo Jose - 5 years, 8 months ago

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It won't matter on the number of digits the final and correct answer has. What matters most is the correct procedure. With all due respect sir, you're highly mistaken.

Danrey Vallejos - 5 years, 8 months ago
Achille 'Gilles'
Aug 10, 2015

Exponents must be resolved starting from the highest level:

= 2^(2^(2^(2^0)))

= 2^(2^(2^1))

= 2^(2^2)

= 2^4

= 16

Finally, someone puts it in terms that are easy to understand. It looks like the confusion was between people treating it as (((2^2)^2)^2)^0 (which is apparently incorrect), and those treating it as 2^(2^(2^(2^0))) (which is correct).

Thanks for clearing that up, Achille!

Leland Jory - 5 years, 8 months ago

X = 2^2^2^2^0

Y = 2^2^2^2

X = Y^0

log X = 0 log Y

log X = 0

X = 1

Rudi Simanoengkalit - 5 years, 9 months ago

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https://www.google.com/search?q=2%5E2%5E2%5E2%5E0&rlz=1CAACAG enUS657US657&oq=2%5E2%5E2%5E2%5E0&aqs=chrome..69i57.1507j0j7&sourceid=chrome&es sm=93&ie=UTF-8 I looked it up in google...google itself says 16 look up the exact problem in the search bar and it gives u 16

Joe Lach - 5 years, 8 months ago

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This is very helpful, thanks. Also, props to google!

searching google for: (((((2)^2)^2)^2)^0) equals 1, while searching google for: 2^2^2^2^0 equals 16.

Adam Houston - 5 years, 7 months ago
Amisha Gupta
May 24, 2014

If you start solving from the top, so, 2 to the power 0 is 1. Then 2 to the power of 1 is 2. Then you can simply solve the problem.

Why can't we start solving it from the bottom instead of the top?

Akagami Ng - 6 years, 12 months ago

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if there would be brackets on (2) then we would have to start from bottom .

Ayush Parasar - 6 years, 12 months ago

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any rule their to solve according to brackets i dont know so plz reply

Gopal Guguloth - 6 years, 12 months ago

thanks! now i understood

Ajay Kr - 6 years, 10 months ago

please search on Tetration, you can find answers there regarding with your question

Danrey Vallejos - 5 years, 9 months ago

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If I say 2^2, it means 2 2; similarly for 2^2^2, (2 2) (2 2) or 2^4=2 2 2*2 but what does exactly mean by 2^2^0 ? Please answer me with explanation, I really want to know ....thanks in advance

Sheikh Rafi - 5 years, 8 months ago

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@Sheikh Rafi you really missed that chapter of your algebra lesson Mr. Sheikh Rafi. 2^2 is 4, not 22. Sorry if I am misled with your text but it's not true. But with regards to your question, in PEMDAS rule, we cannot solve for 2^2^2^2 from the bottom because it has to do simplification first from the topmost exponent. PEMDAS means Parentheses, Exponent, MDAS. You go first with the problems inside the parentheses before with the exponent. In this context, we only have the exponent problem. So you're going to simplify first the topmost exponent. For example, 2^3^4 means 2^81 not 8^4, right? Are they the same? No. Because when you start from the bottom, it will lead you obviously to a surely wrong answer. I hope I taught you a lesson.

Danrey Vallejos - 5 years, 8 months ago

2 2 2 2 0 = 2 2 2 1 2 2 2 2 0 = 2 2 2 2 2 2 2 0 = 2 4 2 2 2 2 0 = 16 \large { 2 }^{ { 2 }^{ { 2 }^{ { 2 }^{ 0 } } } }={ 2 }^{ { 2 }^{ { 2 }^{ 1 } } }\\ { 2 }^{ { 2 }^{ { 2 }^{ { 2 }^{ 0 } } } }={ 2 }^{ { 2 }^{ 2 } }\\ { 2 }^{ { 2 }^{ { 2 }^{ { 2 }^{ 0 } } } }={ 2 }^{ 4 }\\ { 2 }^{ { 2 }^{ { 2 }^{ { 2 }^{ 0 } } } }=16

Oon Han
Jul 7, 2019

Evaluate from top to bottom, not bottom to top ! 2 2 2 2 0 = 2 2 2 1 = 2 2 2 = 2 4 = 16 \begin{aligned} 2^{2^{2^{2^0}}} &= 2^{2^{2^1}} \\ &= 2^{2^2} \\ &= 2^4 \\ &= \boxed{16} \end{aligned}

Therefore, the answer is 16 .

Don Weingarten
Feb 3, 2019

2 to the 0 power, like anything to the 0 power, is 1. Thus this problem reduces to 2 to the power of (2 to the power of 2) = 2 to the power of 4 = 16

Evan Simarmata
Dec 29, 2016

The indices are always in the form of a^b = c. It means the base (a) is at the bottom of its form. The rest (b) remains as the exponent (index). Determine the exponent by calculating the exponentials. You must get c = 16, which is the result.

Prokash Shakkhar
Sep 3, 2016

We can calculate from up to the down.. i.e. 2^0 =1, 2^1=2, 2^2= 4, 2^4=16....

Here, 2^0=1 and 2^2=4 ; so 2^4 = 16

Suman Kumar
Nov 29, 2015

In my views: Right now assume there is two solution of this problem 1 and 16. But we know it can't. So, we will check which one is correct. Assume given problem is x=((((2)^2)^2)^2)^0. Now we will take log of base 2 like this, log(x)=(((2)^2)^2)^0*log2 (it's been difficult to write proper expression of mathematics through mobile so sorry for that and here base of each log is 2 so log2=1).now log2=1,hence log(x)=(((2)^2)^2)^0. Similarly take log again like this, log(log(x))=((2)^2)^0. Next is log(log(log(x)))=2^0. Next log(log(log(log(x))))=0. Now select x=1 and check whether log is existing or not, so log(1)=0, but log(0)=???? It will not exist so, here 1 can't be the answer. Now check for 16, due to base of log is 2, so we will write 16=2^4, take log, log(16)=4, log(log(16))=2, log(log(log(16)))=1, and log(log(log(log(16))))=0. Hence 16 will be answer not 1.

Thanks Suman

So that is why we do it that way!

Zoe Codrington - 2 years, 6 months ago
Scott Riley
Nov 2, 2015

For all maths calculations you must follow BODMAS/BIDMAS before using any other rules. There are no brackets which means that indices are dealt with first. This results in starting at the top of the tower and working your way down which means that the answer is indeed 16.

Sai Ram
Oct 3, 2015

Many people simplify the expression as follows :

2 2 2 2 0 = ( 2 2 ) 2 ) 2 ) 0 . \LARGE {2^{2^{2^{2^0}}} = (2^{2})^{2})^{2})^{0}}.

According to this it's right to use the property ( a m ) n = a m n (a^m)^n = a^{mn}

This results in 2 0 , 2^0, which is 1. 1.

In the problem brackets are not given , hence considering it like that is not right.

While simplifying towers of exponents like this one , we should start evaluating from the top and not from bottom.

2 2 2 2 0 = 2 ( 2 2 ) = 2 4 = 16 \LARGE {2^{2^{2^{2^0}}}} = 2^{(2^2)} = 2^4 = \boxed{16}

William Adams
Oct 3, 2015

So, this problem is confusing a lot of people.

You must break this down because the way it is written the rule (x^y)^z = x^(y*z) does not apply because it is not written that way.

So to simplify this you must start with the highest powers.

So the correct way to solve 2^2^2^2^0is: 2^0 = 1 Then 2^1 = 2 then 2^2 = 4 then 2^4 = 16

You must reduce the tower to a single level starting at the top and working your way down.

The answer is 16. Not 1. Google tetration and you will see that that is what this problem is. This is not a base raised to 2 exponents (as it would be (2^3)^2).

This is an exponent being raised to another exponent. So in order to simplify the base you have to know what the number it's being raised to it. BUT in order to know that number, you have to raise the exponent to its' exponent, and so on and so forth.

The fact that the exponents are not all on the same level should be a big clue that this is not simply multiplying exponents.

Daniel C
Oct 2, 2015

if you hover the mouse over the expression it reveals {2 ^ {2 ^ {2 ^ {2 ^ 0}}}}. The inmost operators are resolved first, so = {2 ^ {2 ^ {2 ^ 1}}} = {2 ^ {2 ^ 2}} = 2 ^ 4 = 16

You actually worked it out this way?

Zoe Codrington - 2 years, 6 months ago

First, solve 2^0. That will give you 1. Then, solve 2^(2^0). That will give you 2^1=2. Now, solve 2^[2^(2^0)]. That will give you 4. Finally, solve 2^{2^[2^(2^0)]}. That will give 2^4=16.

Sadasiva Panicker
Sep 18, 2015

Rule is solve from top. So Answer is 16

Harris Hanley
Sep 15, 2015

2 0 2^{0} = 1 therefore 2 2 2^{2} 2 ^{2} 2 ^{2} 0 ^{0} = 2 2 2^{2} 2 ^{2} 1 ^{1} and 2 1 2^{1} = 2 so 2 2 2^{2} 2 ^{2} 1 ^{1} = 2 2 2^{2} 2 ^{2} = 2 4 2^{4} = 16

Dominic Parnell
Sep 14, 2015

2^2^2^2^0=2^2^2^1=2^2^2=2^4=16 (you can check this with a calculator too for those that don't believe this to be correct and the answer to be 1). you start with 2^0=1 then move down to 2^1=2 then move down again to 2^2 leaving you with 2^4=16. BODMAS.

Hadia Qadir
Aug 12, 2015

2^2^2^2^0= 2^2^2^1= 16, so answer is 16 smile emoticon

Fred Tagamolila
Aug 11, 2015

My analysis here is purely by inspection and logic. One can mentally raise 2 to the 6th power which makes it 16. Then , since the last power is 0, you can discard it , stop right there and you don't do any operation anymore. Therefore, the answer is your last answer which is 16.

2^6 is not 16. It is 64. if it was [[(2^2)^2]^2]^0 then it will be 1, since there's no brackets you start from the top and the answer is 2^4 which is 16.

Andrew Richard Thapa - 5 years, 9 months ago

This is an incorrect method:you can’t just add the powers!

Zoe Codrington - 2 years, 6 months ago
Mmk Majid khan
Aug 10, 2015

this is a perplexing question. but the thing to remember in this question is the rule of exponents. just come from top to bottom u will get the answer ((2)^(((2)^(((2)^(((2)^(0))))))))=((2)^(((2)^(((2)^(1))))))=((2)^(((2)^(2))))=((2)^(4))=16

better show parenthesis. the question could have been more clear. !!..LOL..

Brijesh Naik - 5 years, 7 months ago

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