Power Prep Question

This topic has expert replies
Source: — Problem Solving |

Master | Next Rank: 500 Posts
Posts: 165
Joined: Wed May 28, 2008 11:25 pm
Thanked: 9 times
GMAT Score:730

by sumithshah » Fri Aug 15, 2008 3:05 am
OA is E btw

Legendary Member
Posts: 661
Joined: Tue Jul 08, 2008 12:58 pm
Location: France
Thanked: 48 times

by pepeprepa » Fri Aug 15, 2008 3:41 am
sqrt(4)=2
4^(1/4)=(2^2^)^(1/4)=2^(1/2)=sqrt(2)= more or less 1.4
4^(1/3)= more or less 1.6 by searching a little

The toal is greater than 4.
But anyway you are sure that the result is at least 3.4 thanks to sqrt(4) and 4^(1/4)=sqrt(2)=1.4
And you are also sure that 4^(1/3) is between 1 and 2 so it is greater than 4

Master | Next Rank: 500 Posts
Posts: 165
Joined: Wed May 28, 2008 11:25 pm
Thanked: 9 times
GMAT Score:730

by sumithshah » Fri Aug 15, 2008 4:10 am
Ah! completely missed the 4 = 2^2 part!
thanks

Senior | Next Rank: 100 Posts
Posts: 48
Joined: Fri Aug 08, 2008 4:44 am
Thanked: 4 times
GMAT Score:750

by santa_dem » Fri Aug 15, 2008 5:18 am
Without any great math knwoledge, you should know at least that

4^(1/2)=2

x^(1/y)=1 for any x and y, and if x>1, then x^(1/y)>1

so 2+1+...+1+...>4