Check GMAT Club Decision Tracker for the Latest School Decision Releases https://gmatclub.com/AppTrack

 It is currently 28 May 2017, 11:38

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

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

GMAT Diagnostic Test Question 2

Author Message
Founder
Joined: 04 Dec 2002
Posts: 14961
Location: United States (WA)
GMAT 1: 750 Q49 V42
GPA: 3.5
Followers: 3961

Kudos [?]: 25201 [0], given: 4765

GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

06 Jun 2009, 19:03
Expert's post
5
This post was
BOOKMARKED
GMAT Diagnostic Test Question 2
Field: Arithmetic, Square Roots
Difficulty: 600

$$\sqrt{36+64+5^2} + \sqrt{20} = ?$$

A. $$19 + \sqrt{20}$$
B. $$19\sqrt{20}$$
C. $$\sqrt{145}$$
D. $$5\sqrt{100}+\sqrt{20}$$
E. $$7\sqrt{5}$$
_________________

Founder of GMAT Club

US News Rankings progression - last 10 years in a snapshot - New!
Just starting out with GMAT? Start here...
Need GMAT Book Recommendations? Best GMAT Books

Co-author of the GMAT Club tests

Last edited by Bunuel on 07 Oct 2013, 00:02, edited 1 time in total.
Edited the difficulty.
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2013
Followers: 163

Kudos [?]: 1828 [3] , given: 376

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 14:52
3
KUDOS
2
This post was
BOOKMARKED
l0rrie wrote:
I feel so stupid among you guys lol.. Was I really the only one that picked A?

Why is that wrong anyways.. I mean if you square root everything under it it just becomes the number itself right.. * Huge sigh *

$$\sqrt{1+2-3+5-5+9} \ne \sqrt{1}+\sqrt{2}-\sqrt{3}+\sqrt{5}-\sqrt{5}+\sqrt{9}$$

If you see multiple addition or subtraction under the root, make sure you simplify that first and take square root of the total.

$$\sqrt{1+2-3+5-5+9} = \sqrt{9} = 3$$

However,
$$\sqrt{mn} = \sqrt{m}*\sqrt{n}$$

For addition and subtraction, one can't split the terms as individual root term. And also the vice versa is not allowed(two split root terms can't be combined under one root)

For multiplication and division, one can split the terms as individual root term. Vice versa is also true.

$$\sqrt{36+64+5^2}+\sqrt{20}=\sqrt{125}+\sqrt{20}=\sqrt{5^2*5}+\sqrt{2^2*5}=5\sqrt{5}+2\sqrt{5}=7\sqrt{5}$$

Ans: "E"
_________________
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2013
Followers: 163

Kudos [?]: 1828 [1] , given: 376

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

25 May 2011, 01:39
1
KUDOS
MitDavidDv wrote:
I actually didn't get why you eliminated A, B, D. I think this method would be dangerous. Solving it entirely is better. Shouldn't take you more than 45 seconds if you practice a bit.

What if the question was:
\sqrt{9^2+5^3+10^2+55}+\sqrt{20}

Shalom. I eliminated A, B, and D because they contain the sqrt{20} unsimplified. I am sure that solving it would be better I agree. I am only pointing out that I noticed A, B, and D could possibly be done away with using the process of elimination. The remaining two answers have the sqrt{20} broken down. If the question was \sqrt{9^2+5^3+10^2+55}+\sqrt{20} then I would consider the answer choices with the sqrt{20} simplified.

$$\sqrt{9^2+5^3+10^2+55}+\sqrt{20} = 19+\sqrt{20}$$

I wouldn't advocate to guess in these simplify type of questions. Save the guessing and POE for relatively difficult questions.

_________________
Founder
Joined: 04 Dec 2002
Posts: 14961
Location: United States (WA)
GMAT 1: 750 Q49 V42
GPA: 3.5
Followers: 3961

Kudos [?]: 25201 [0], given: 4765

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

06 Jun 2009, 19:16
Expert's post
1
This post was
BOOKMARKED
Explanation:
 Rating:

$$\sqrt{36+64+5^2} + \sqrt{20} =$$

$$\sqrt{125} + \sqrt{20} =$$

$$\sqrt{25*5} + \sqrt{4*5} =$$

$$5\sqrt{5} + 2\sqrt{5} =$$

$$7\sqrt{5}$$
_________________

Founder of GMAT Club

US News Rankings progression - last 10 years in a snapshot - New!
Just starting out with GMAT? Start here...
Need GMAT Book Recommendations? Best GMAT Books

Co-author of the GMAT Club tests

Manager
Joined: 24 Jul 2009
Posts: 192
Location: Anchorage, AK
Schools: Mellon, USC, MIT, UCLA, NSCU
Followers: 4

Kudos [?]: 42 [0], given: 10

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

26 Nov 2009, 08:15
Made a stupid mistake and really shouldn't have since I factored 20 right away! Figured that 5 under the radical would matter and it did. Will go w/ my gut next time.
_________________

Reward wisdom with kudos.

Manager
Joined: 24 Jul 2009
Posts: 192
Location: Anchorage, AK
Schools: Mellon, USC, MIT, UCLA, NSCU
Followers: 4

Kudos [?]: 42 [0], given: 10

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

11 Jan 2010, 21:46
gottabwise wrote:
Made a stupid mistake and really shouldn't have since I factored 20 right away! Figured that 5 under the radical would matter and it did. Will go w/ my gut next time.

Just reworked problem. Remembered that I had to add the numbers under the radical before I could simplify anything.
_________________

Reward wisdom with kudos.

Intern
Joined: 18 Dec 2009
Posts: 3
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

23 Jan 2010, 02:42
This one was pretty easy.....
Manager
Joined: 10 Jan 2010
Posts: 186
Location: Germany
Concentration: Strategy, General Management
Schools: IE '15 (M)
GPA: 3
WE: Consulting (Telecommunications)
Followers: 2

Kudos [?]: 30 [0], given: 7

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

02 Feb 2010, 12:01
Good question, but really simple. Good practice anyway..
Director
Joined: 21 Dec 2009
Posts: 585
Concentration: Entrepreneurship, Finance
Followers: 18

Kudos [?]: 705 [0], given: 20

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

02 Apr 2010, 04:21
Got this right away. This question -700 difficulty level- appears a little easier
than question1- 650 level.

Buddy, thanks a bunch for your efforts.
_________________

KUDOS me if you feel my contribution has helped you.

Intern
Joined: 17 Apr 2010
Posts: 1
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

17 Apr 2010, 17:58
Hey,

Not sure I agree this was easier than Q1, but I must question the difficulty level. How is this "700" level derived...?
Manager
Joined: 06 Apr 2010
Posts: 82
Followers: 2

Kudos [?]: 40 [0], given: 2

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

20 May 2010, 11:03
A lot easier than the first one. I would say 500-600 level?
Intern
Joined: 22 May 2010
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 1

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

26 May 2010, 11:33
Why can't the answer be D? Is it not factored enough?
Intern
Joined: 05 Jun 2009
Posts: 2
Followers: 0

Kudos [?]: 0 [0], given: 0

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

07 Sep 2010, 12:27
The first part of D, 5 times sqrt of 100, is impossible to get if you factored correctly. If you add up all three terms you should get 125. The sq. root of 125 can be broken down into the square root of (5 x 5 x 5).
Manager
Joined: 28 Jan 2011
Posts: 76
Location: Tennessee
Schools: Belmont University
Followers: 2

Kudos [?]: 171 [0], given: 73

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

05 May 2011, 07:48
1
This post was
BOOKMARKED
Shalom
[b]Tell me if I am wrong but if I had to make an educated guess on this question I would chose E. If you breakdown the sqrt(20) that leaves 2*sqrt(5). The only possible answer would be E simply because three of the other four possible answers include the sqrt(20) unsimplified.
[/b]
Manager
Joined: 16 Mar 2011
Posts: 177
Followers: 1

Kudos [?]: 42 [0], given: 13

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 14:30
I feel so stupid among you guys lol.. Was I really the only one that picked A?

Why is that wrong anyways.. I mean if you square root everything under it it just becomes the number itself right.. * Huge sigh *
Manager
Joined: 16 Mar 2011
Posts: 177
Followers: 1

Kudos [?]: 42 [0], given: 13

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 14:53
Aaah I get it.. Aargh my math basics are still horrible after so many weeks of studying.. Thanks, fluke.. you save the day... AGAIN..
Manager
Joined: 28 Jan 2011
Posts: 76
Location: Tennessee
Schools: Belmont University
Followers: 2

Kudos [?]: 171 [0], given: 73

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 14:58
Shalom
[b]Tell me if I am wrong but if I had to make an educated guess on this question I would chose E. If you breakdown the sqrt(20) that leaves 2*sqrt(5). By using the process of elimination you can get rid of three of the four possible answers. That would leave C and E. Then if I would have had to make a choice between these two I would chose E because it is the most simplified.
Math Forum Moderator
Joined: 20 Dec 2010
Posts: 2013
Followers: 163

Kudos [?]: 1828 [0], given: 376

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 15:09
MitDavidDv wrote:
Shalom
[b]Tell me if I am wrong but if I had to make an educated guess on this question I would chose E. If you breakdown the sqrt(20) that leaves 2*sqrt(5). By using the process of elimination you can get rid of three of the four possible answers. That would leave C and E. Then if I would have had to make a choice between these two I would chose E because it is the most simplified.

I actually didn't get why you eliminated A, B, D. I think this method would be dangerous. Solving it entirely is better. Shouldn't take you more than 45 seconds if you practice a bit.

What if the question was:
$$\sqrt{9^2+5^3+10^2+55}+\sqrt{20}$$
_________________
Manager
Joined: 28 Jan 2011
Posts: 76
Location: Tennessee
Schools: Belmont University
Followers: 2

Kudos [?]: 171 [0], given: 73

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

24 May 2011, 21:54
I actually didn't get why you eliminated A, B, D. I think this method would be dangerous. Solving it entirely is better. Shouldn't take you more than 45 seconds if you practice a bit.

What if the question was:
\sqrt{9^2+5^3+10^2+55}+\sqrt{20}

Shalom. I eliminated A, B, and D because they contain the sqrt{20} unsimplified. I am sure that solving it would be better I agree. I am only pointing out that I noticed A, B, and D could possibly be done away with using the process of elimination. The remaining two answers have the sqrt{20} broken down. If the question was \sqrt{9^2+5^3+10^2+55}+\sqrt{20} then I would consider the answer choices with the sqrt{20} simplified.
Manager
Joined: 28 Jan 2011
Posts: 76
Location: Tennessee
Schools: Belmont University
Followers: 2

Kudos [?]: 171 [0], given: 73

Re: GMAT Diagnostic Test Question 2 [#permalink]

Show Tags

25 May 2011, 06:27
Shalom
Yes I will save the guessing for the harder questions.
Re: GMAT Diagnostic Test Question 2   [#permalink] 25 May 2011, 06:27

Go to page    1   2    Next  [ 27 posts ]

Similar topics Replies Last post
Similar
Topics:
40 GMAT Diagnostic Test Question 7 31 29 Jan 2014, 02:33
9 GMAT Diagnostic Test Question 6 30 08 Jan 2013, 04:21
42 GMAT Diagnostic Test Question 5 26 20 Jun 2014, 03:49
16 GMAT Diagnostic Test Question 4 37 09 Apr 2014, 06:43
25 GMAT Diagnostic Test Question 3 33 22 Oct 2013, 23:26
Display posts from previous: Sort by

GMAT Diagnostic Test Question 2

Moderator: Bunuel

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.