Last visit was: 24 Apr 2024, 20:39 It is currently 24 Apr 2024, 20:39

Close
GMAT Club Daily Prep
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.
Close
Request Expert Reply
Confirm Cancel
SORT BY:
Date
Tags:
Show Tags
Hide Tags
Math Expert
Joined: 02 Sep 2009
Posts: 92900
Own Kudos [?]: 618834 [28]
Given Kudos: 81588
Send PM
Most Helpful Reply
RC & DI Moderator
Joined: 02 Aug 2009
Status:Math and DI Expert
Posts: 11170
Own Kudos [?]: 31894 [6]
Given Kudos: 290
Send PM
General Discussion
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18756
Own Kudos [?]: 22049 [3]
Given Kudos: 283
Location: United States (CA)
Send PM
Manager
Manager
Joined: 30 Nov 2018
Posts: 64
Own Kudos [?]: 8 [0]
Given Kudos: 194
Send PM
Re: What is the decreasing order from left to right of the following numbe [#permalink]
chetan2u wrote:
What is the decreasing order from left to right of the following numbers?

\(\sqrt[4]{3}, \sqrt[5]{6},\sqrt[10]{12},\sqrt[15]{45}\)

Let us get all the terms without roots, so raise each to the power of LCM(4,5,10,15) = 60
\(\sqrt[4]{3}, \sqrt[5]{6},\sqrt[10]{12},\sqrt[15]{45}\)=\(3^{15},6^{12},12^{6},45^4\)
(I) let us check between \(3^{15},6^{12}\)
\(3^{15}=3^{12}*3^3\) and \(6^{12}=3^{12}*2^{12}=3^{12}*(2^4)^3=3^{12}*16^3\).....\(3^{15}<6^{12}...\sqrt[4]{3}<\sqrt[5]{6}.\)..
Choices A and E can be eliminated
Similarly we can test other pairs..

Another way to test \(3^{15},6^{12},12^{6},45^4\) is to try to get them in same power
\(3^{15}=(3^5)^3=243^3,6^{12}=(6^4)^3=(1296)^3,12^{6}=(12^2)^3=(144)^3,45^4\)...
So, descending order \( \sqrt[5]{6},\sqrt[4]{3},\sqrt[10]{12},\), and we have to check where \(\sqrt[15]{45}\) fits in...
\(6^{12}=(6^3)^4=216^4,45^4\)......6^{12} >45^4
\(12^{6}=(12^3)^2=1728^2,45^4=(45^2)^2=(2025)^2.....45^4>12^6\)
\(3^{15}=3^8*3^7=3^8*3*(3^3)^2=3^8*3*27^2,45^4=3^8*5^4=3^8*25^2......3^{15}>45^4\)


(D) \(\sqrt[5]{6}, \sqrt[4]{3}, \sqrt[15]{45}, \sqrt[10]{12}\)


but is it alright to treat 1/n roots as n roots ?
RC & DI Moderator
Joined: 02 Aug 2009
Status:Math and DI Expert
Posts: 11170
Own Kudos [?]: 31894 [2]
Given Kudos: 290
Send PM
Re: What is the decreasing order from left to right of the following numbe [#permalink]
2
Kudos
Expert Reply
sthahvi wrote:
chetan2u wrote:
What is the decreasing order from left to right of the following numbers?

\(\sqrt[4]{3}, \sqrt[5]{6},\sqrt[10]{12},\sqrt[15]{45}\)

Let us get all the terms without roots, so raise each to the power of LCM(4,5,10,15) = 60
\(\sqrt[4]{3}, \sqrt[5]{6},\sqrt[10]{12},\sqrt[15]{45}\)=\(3^{15},6^{12},12^{6},45^4\)
(I) let us check between \(3^{15},6^{12}\)
\(3^{15}=3^{12}*3^3\) and \(6^{12}=3^{12}*2^{12}=3^{12}*(2^4)^3=3^{12}*16^3\).....\(3^{15}<6^{12}...\sqrt[4]{3}<\sqrt[5]{6}.\)..
Choices A and E can be eliminated
Similarly we can test other pairs..

Another way to test \(3^{15},6^{12},12^{6},45^4\) is to try to get them in same power
\(3^{15}=(3^5)^3=243^3,6^{12}=(6^4)^3=(1296)^3,12^{6}=(12^2)^3=(144)^3,45^4\)...
So, descending order \( \sqrt[5]{6},\sqrt[4]{3},\sqrt[10]{12},\), and we have to check where \(\sqrt[15]{45}\) fits in...
\(6^{12}=(6^3)^4=216^4,45^4\)......6^{12} >45^4
\(12^{6}=(12^3)^2=1728^2,45^4=(45^2)^2=(2025)^2.....45^4>12^6\)
\(3^{15}=3^8*3^7=3^8*3*(3^3)^2=3^8*3*27^2,45^4=3^8*5^4=3^8*25^2......3^{15}>45^4\)


(D) \(\sqrt[5]{6}, \sqrt[4]{3}, \sqrt[15]{45}, \sqrt[10]{12}\)


but is it alright to treat 1/n roots as n roots ?



Hi

All the terms are positive and more than 1.
Property of all the numbers greater than 1 is that as you increase the power, the number becomes larger. Also, larger the number, the larger it will become when raised to same power as a smaller number than that.
So if \(\sqrt[3]{x} \) and \(\sqrt[4]{y}\) are raised to SAME power, the value of whichever of the terms was initially more will remain more.
Using this property, we raise them to a bigger power to simply the terms.
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 32658
Own Kudos [?]: 821 [0]
Given Kudos: 0
Send PM
Re: What is the decreasing order from left to right of the following numbe [#permalink]
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
Re: What is the decreasing order from left to right of the following numbe [#permalink]
Moderators:
Math Expert
92900 posts
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne