Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 350,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: If x,y are numbers >0 and 2^x*5^y=400 [#permalink]
04 May 2013, 17:32

1

This post received KUDOS

Zarrolou wrote:

If \(x,y\) are numbers \(>0\) and \(2^x*5^y=400\), what could be the value of \(x\)?

I)2 II)3 III)4

A)Only I B)Only II C)I and II D)Only III E)I, II and III

Hi guys, this is my first PS question hope you like it, any feedback is appreciated.

I'll post the OA and the OE after some discussion. Kudos to the first ones who got it right! (BTW: it's not as easy as it seems, it mays tricks you...)

I am getting E

You can make it into \sqrt{2^x} * \sqrt{5^y} =20

given that all numbers are >0

Therefor x=2 x^2*5^1=20 2 works

and when x=4 gives you 16*25=400

if x=3 it comes out to 2\sqrt{2}*5\sqrt{2}=400 _________________

Re: If x,y are numbers >0 and 2^x*5^y=400 [#permalink]
04 May 2013, 20:42

Zarrolou wrote:

If \(x,y\) are numbers \(>0\) and \(2^x*5^y=400\), what could be the value of \(x\)?

I)2 II)3 III)4

A)Only I B)Only II C)I and II D)Only III E)I, II and III

Hi guys, this is my first PS question hope you like it, any feedback is appreciated.

I'll post the OA and the OE after some discussion. Kudos to the first ones who got it right! (BTW: it's not as easy as it seems, it mays tricks you...)

First we represent 400 in its prime factored form. \(400 = 4 * 100 = 2^2 * 2^2 * 5^2 = 2^4 * 5^2\) Hence \(x = 4\) is the only possible value. Correct option is D

Re: If x,y are numbers >0 and 2^x*5^y=400 [#permalink]
04 May 2013, 21:48

Zarrolou wrote:

If \(x,y\) are numbers \(>0\) and \(2^x*5^y=400\), what could be the value of \(x\)?

I)2 II)3 III)4

A)Only I B)Only II C)I and II D)Only III E)I, II and III

\(2^x*5^y=400\) Substituting x=2,3,4 in the given equation I) 2 --> \(2^2*5^y=400\); \(5^y=100\) --> Not possible II) 3 --> \(2^3*5^y=400\); \(5^y=50\) --> Not possible III) 4 --> \(2^4*5^y=400\); \(5^y=25\) , so y =2--> Correct

IMO Answer: D _________________

Consider giving +1 Kudo when my post helps you. Also, Good Questions deserve Kudos..!

Harvard asks you to write a post interview reflection (PIR) within 24 hours of your interview. Many have said that there is little you can do in this...