BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

A difficult math, pls help to explain

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3835
Joined: Fri Apr 02, 2010 10:00 pm
Location: Milpitas, CA
Thanked: 1854 times
Followed by:523 members
GMAT Score:770

by Anurag@Gurome » Sat Sep 03, 2011 3:57 am
tracyyahoo wrote:if 2^x+2^x+2^x+2^x=2^n, what is x in terms of n?
--> 2^x+2^x+2^x+2^x = 2^n
--> 4*(2^x) = 2^n
--> (2^2)*(2^x) = 2^n
--> 2^(x+2) = 2^n

Hence, x = n - 2

The correct answer is D.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 359
Joined: Wed Mar 11, 2009 4:37 am
Location: Kolkata, India
Thanked: 50 times
Followed by:2 members

by Abhishek009 » Sat Sep 03, 2011 6:33 am
tracyyahoo wrote:if 2^x+2^x+2^x+2^x=2^n, what is x in terms of n?

a)n/4
b)4n
c)2n
d)n-2
e)n+2

pls explain
Plug in some values of x to find the value of n and get the pattern....


Let x be 0

Then ,

2^x+2^x+2^x+2^x = 2^n

2^0+2^0+2^0+2^0 = 2^2

So n = 2 ; when x = 0


Let x be 1

Then ,

2^x+2^x+2^x+2^x = 2^n

2^1+2^1+2^1+2^1 = 2^3

So n = 3 ; when x is 1


Now U can easily derive the pattern ,

n = x + 2

or x = n - 2.
Abhishek
Top
Post new topic Post Reply
• Page 1 of 1