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GMAT Diagnostic Test Question 1

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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 26 Aug 2011, 08:10
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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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 13 Feb 2012, 15:18
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??
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 13 Feb 2012, 15:26
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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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 04 Sep 2012, 09:43
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.
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 04 Sep 2012, 10:56
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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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 19 Sep 2012, 20:54
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
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 26 Apr 2013, 11:46
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??


Correct answer is :
=> 324^(1/2) + 289^(1/2) = 18+17 = 35
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 26 Apr 2013, 15:43
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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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 04 Oct 2013, 02:12
\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.

So, the answer is D.
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 14 Apr 2014, 01:37
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? :?:
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Re: GMAT Diagnostic Test Question 1 [#permalink] New post 14 Apr 2014, 01:53
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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.
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Re: GMAT Diagnostic Test Question 1   [#permalink] 14 Apr 2014, 01:53
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