GMATprep: exponent

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nhai2003: Senior | Next Rank: 100 Posts; Posts: 75; Joined: Tue Feb 10, 2009 11:30 pm

by nhai2003 » Mon Jun 08, 2009 5:02 pm

Anyone please explain to me why the answer is 2^8,
I did it again and again, it still 2^5

2^(4-1)^2/2^(3-2) =

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Source: Beat The GMAT — Problem Solving | Mon Jun 08, 2009 5:02 pm

raleigh: Master | Next Rank: 500 Posts; Posts: 103; Joined: Mon May 18, 2009 9:47 am; Thanked: 19 times

by raleigh » Mon Jun 08, 2009 5:31 pm

The answer is 2^5.

2^(4-1)^2/2^(3-2) =

2^(3)^2/2^1 =

2^(2*3)/2 =

2^6/2 =

2^5

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Musiq: Senior | Next Rank: 100 Posts; Posts: 93; Joined: Thu Apr 10, 2008 1:42 pm; Location: Chicago; Thanked: 20 times

Re: GMATprep: exponent

by Musiq » Mon Jun 08, 2009 5:47 pm

nhai2003 wrote:Anyone please explain to me why the answer is 2^8,
I did it again and again, it still 2^5

2^(4-1)^2/2^(3-2) =

This is a VERY good problem...classic GMAT.

Please see the examples below and use PEMDAS ( BODMAS for British System).

(X) ^2^3 = (X) 2*3 = (X)^6
We focussed on the Paranthesis first and then moved onto the Exponent.

Now, observe the below question:

X ^ (2) ^3 = X ^(8)

Since Paranthesis has to be dealt with first, this is really x to the power of 2 cubed...or X to the power of 8.

Please let me know if this clears up the question for you.

For love, not money.

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nhai2003: Senior | Next Rank: 100 Posts; Posts: 75; Joined: Tue Feb 10, 2009 11:30 pm

by nhai2003 » Mon Jun 08, 2009 6:00 pm

Musiq,

With your explanation, the answer: 2^(4-1)^2/2^(3-2) = would be 2^7

while OA: 2^8

or I'm getting crazy???

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Musiq: Senior | Next Rank: 100 Posts; Posts: 93; Joined: Thu Apr 10, 2008 1:42 pm; Location: Chicago; Thanked: 20 times

by Musiq » Mon Jun 08, 2009 6:12 pm

nhai2003 wrote:Musiq,

With your explanation, the answer: 2^(4-1)^2/2^(3-2) = would be 2^7

while OA: 2^8

or I'm getting crazy???

That's alrite nhai...as long as you get the concept we can come up with the answer.

Given Question is a fraction....let's deal with the denominator first.

Denominator = 2^ (3-2) = 2^1
Numerator = 2 ^ (4-1) ^2 = 2 ^ (3)^2 = 2 ^9

Therefore, the answer = 2^9 divided by 2^ 1 = 2^8.

Please let me know if this clarifies things.

For love, not money.

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ssmiles08: Master | Next Rank: 500 Posts; Posts: 472; Joined: Sun Mar 29, 2009 6:54 pm; Thanked: 56 times

by ssmiles08 » Mon Jun 08, 2009 7:03 pm

raleigh wrote:The answer is 2^5.

2^(4-1)^2/2^(3-2) =

2^(3)^2/2^1 =

2^(2*3)/2 =

2^6/2 =

2^5

@raleigh I made the same assumption a while ago, but I believe one of the users cramya clarified why its not (2*3)

https://www.beatthegmat.com/exponents-gm ... 38128.html

1) a^b^c with no parentheses do b^c first and then raise a to that

2) (a^b)^c = a^ (b*c)

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