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# GMAT Diagnostic Test Question 1

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Intern
Joined: 12 Jan 2011
Posts: 3

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Re: GMAT Diagnostic Test Question 1 [#permalink]

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26 Aug 2011, 09:10
this ques is very eazy but difficult if don't know you perfect squares.
I was able to get the first part very quick but I used calculator for the second part
which is not allowed in the GMAT Exams

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Intern
Joined: 13 Feb 2012
Posts: 20

Kudos [?]: 58 [0], given: 14

WE: Other (Transportation)
Re: GMAT Diagnostic Test Question 1 [#permalink]

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13 Feb 2012, 16:18
LU wrote:
Based on Math formula its 324 - 289 = 35

And it works for any number regardless if it is perfect square or not.

Thanks
LU

Sorry, but 36^(1/2) - 25^(1/2)= 6 - 5 = 1
but 36 - 25 = 11
Do I miss anything about the formula??

Kudos [?]: 58 [0], given: 14

Intern
Joined: 13 Feb 2012
Posts: 20

Kudos [?]: 58 [0], given: 14

WE: Other (Transportation)
Re: GMAT Diagnostic Test Question 1 [#permalink]

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13 Feb 2012, 16:26
If you cannot remember the squares of the first 20 numbers I think the best approach is to play with the units digits only. The root of 324 should end to 2 or 8 and the root of 289 should end to 3 or 7.
The next step is to take those figures in pairs and check the digit of their sum.
So (2,3) --> units digit 5 (Answer D)
(2,7) --> units digit 9 (No Answer)
(8,3) --> units digit 1 (No Answer)
(8,7) --> units digit 5 (Answer D)
I don't even care about which numbers they actually are!

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Intern
Joined: 30 May 2011
Posts: 18

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Re: GMAT Diagnostic Test Question 1 [#permalink]

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04 Sep 2012, 10:43
bb wrote:
GMAT Diagnostic Test Question 1
Diffculty: 650
Field: Arithmetic, Roots
 Rating:

$$\sqrt{324} + \sqrt{289} = ?$$

(A). 32
(B). 33
(C). 34
(D). 35
(E). 36

The Unit digit of square root of 324 is 2, the unit digit for square root of 289 is 3, so the unit digit for the two must be 5, only D fits.

Kudos [?]: 7 [0], given: 4

Intern
Joined: 28 Aug 2012
Posts: 45

Kudos [?]: 48 [0], given: 3

Location: Austria
GMAT 1: 770 Q51 V42
Re: GMAT Diagnostic Test Question 1 [#permalink]

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04 Sep 2012, 11:56
linglinrtw wrote:
The Unit digit of square root of 324 is 2, the unit digit for square root of 289 is 3, so the unit digit for the two must be 5, only D fits.
Correct answer, wrong solution. The unit's digit of square root of 324 can be 8, too. And the unit's digit of square root of 289 can be 7, too.

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Intern
Status: Preparing for GMAT
Joined: 19 Sep 2012
Posts: 19

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Location: India
GMAT Date: 01-31-2013
WE: Information Technology (Computer Software)
Re: GMAT Diagnostic Test Question 1 [#permalink]

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19 Sep 2012, 21:54
Memorise the squares and cubes upto 20...it will help in faster calculation...

else seeing the last digit.. 9 so square root of 7 is 49 so try 17
and same way 4 so 8 * 8 64 ends with 4 also next to 17..

so 17 + 18 = 35.

D
_________________

Rajeev Nambyar
Chennai, India.

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Intern
Joined: 26 Apr 2013
Posts: 1

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

Re: GMAT Diagnostic Test Question 1 [#permalink]

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26 Apr 2013, 12:46
tom09b wrote:
LU wrote:
Based on Math formula its 324 - 289 = 35

And it works for any number regardless if it is perfect square or not.

Thanks
LU

Sorry, but 36^(1/2) - 25^(1/2)= 6 - 5 = 1
but 36 - 25 = 11
Do I miss anything about the formula??

=> 324^(1/2) + 289^(1/2) = 18+17 = 35
-alsukran

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Intern
Joined: 18 Nov 2011
Posts: 36

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Concentration: Strategy, Marketing
GMAT Date: 06-18-2013
GPA: 3.98
Re: GMAT Diagnostic Test Question 1 [#permalink]

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26 Apr 2013, 16:43
LU wrote:
Based on Math formula its 324 - 289 = 35

And it works for any number regardless if it is perfect square or not.

Thanks
LU

"Based on math formula" - To which math formula in particular are you refering? Expand please.

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Intern
Joined: 31 Aug 2013
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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04 Oct 2013, 03:12
$$\sqrt{324} + \sqrt{289} = ?$$

(A). 32
(B). 33
(C). 34
(D). 35
(E). 36[/quote]

324 is the square root of 18 and 289 is the square root of 17.

ie 18 + 17 = 35.

Kudos [?]: 2 [0], given: 1

Intern
Joined: 13 May 2013
Posts: 29

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Re: GMAT Diagnostic Test Question 1 [#permalink]

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14 Apr 2014, 02:37
LU wrote:
Based on Math formula its 324 - 289 = 35

And it works for any number regardless if it is perfect square or not.

Thanks
LU

What is this "Math formula" ?
It works for any number? The square root of 64 + the square root of 25 is NOT equal to 64 - 25.
Or what am I missing here?

Kudos [?]: 10 [0], given: 28

Math Expert
Joined: 02 Sep 2009
Posts: 42249

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Re: GMAT Diagnostic Test Question 1 [#permalink]

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14 Apr 2014, 02:53
1
KUDOS
Expert's post
Saabs wrote:
LU wrote:
Based on Math formula its 324 - 289 = 35

And it works for any number regardless if it is perfect square or not.

Thanks
LU

What is this "Math formula" ?
It works for any number? The square root of 64 + the square root of 25 is NOT equal to 64 - 25.
Or what am I missing here?

Yes, that's not true.
_________________

Kudos [?]: 132643 [1], given: 12326

Re: GMAT Diagnostic Test Question 1   [#permalink] 14 Apr 2014, 02:53

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# GMAT Diagnostic Test Question 1

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