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GMAT Diagnostic Test Question 1

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GMAT Diagnostic Test Question 1 [#permalink]

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05 Jun 2009, 22:30
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GMAT Diagnostic Test Question 1
Diffculty: 550
Field: Arithmetic, Roots

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

(A). 32
(B). 33
(C). 34
(D). 35
(E). 36
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Last edited by Bunuel on 07 Oct 2013, 00:01, edited 1 time in total.
Edited the difficulty.
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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21 Dec 2009, 14:09
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Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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11 Jan 2011, 22:32
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Based on Math formula its 324 - 289 = 35

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

Thanks
LU
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Re: GMAT Diagnostic Test Q1 [#permalink]

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19 Dec 2009, 13:00
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$$\sqrt{324} = \sqrt{2*2*3*3*3*3}=2*3*3=18$$;
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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05 Jul 2011, 08:08
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Let me explain my thought process.

First I looked for the even number, since its easier to find the square root.

So 2*2*9*9 =324 => sqrt(324) = 18

The next number was 289 => sqrt should be odd number.

Then I directly jumped to options, only 33 & 35 are odd. (Since Even(18)+odd = Odd)

33-18 would be 15 and 15 squared is 225.

Ending with the option D) 35.

Hope this helps
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14 Dec 2010, 21:22
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To add to lionslion's technique, if you already solved the square root of the first number to be 18 then by inspection you can tell that the second number has to be 17 and not 13 since square of 13 has to be closer to 100 (10sq = 100) whereas square for 17 has to be closer to 400 (20sq = 400). Since both 13 and 17 are primes, making a known guess would indeed save you tedious calculation on each one one of them.
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Re: GMAT Diagnostic Test Q1 [#permalink]

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05 Jun 2009, 22:31
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Explanation:
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$$\sqrt{324} = 18$$; $$\sqrt{289} = 17$$; $$18 + 17 = 35$$
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Re: GMAT Diagnostic Test Q1 [#permalink]

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21 Dec 2009, 07:50
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I'd recommend remembering the squares of integers up to 20. You'll be able to save some time if you do. If you can't tell what the multiples of a number, you'll have to find them one by one. I doubt there's some magic technique for it .
sunnyvee wrote:
bb wrote:
Explanation:
 Rating:

$$\sqrt{324} = 18$$; $$\sqrt{289} = 17$$; $$18 + 17 = 35$$

this qxn may seem dumb, but what figures did you use for $$\sqrt{289}$$?
plus cud u show shorter way of finding the multiples without having to calculate figure after figure?
hope i make sense
thank you

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Re: GMAT Diagnostic Test Question 1 [#permalink]

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28 Jul 2011, 02:48
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D - 35

The only ^2 that end up with a 4 are 2 or 8, the only ^2 that end up with 9 are 3 or 7

2+9 ends up with 1 at the end
2+3 end up with 5 at the end
8+9 end up with 7
8+3 end up with 1

So the only answer is D - 35 (as it end up with a 5)
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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14 Apr 2014, 02:53
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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 Q1 [#permalink]

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21 Dec 2009, 06:21
bb wrote:
Explanation:
 Rating:

$$\sqrt{324} = 18$$; $$\sqrt{289} = 17$$; $$18 + 17 = 35$$

this qxn may seem dumb, but what figures did you use for [m]\sqrt { 289}?
plus cud u show shorter way of finding the multiples without having to calculate figure after figure?
hope i make sense
thank you
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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22 Dec 2009, 22:25
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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29 Dec 2009, 02:42
lionslion wrote:
Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

cool. that sure helps
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Re: GMAT Diagnostic Test Q1 [#permalink]

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11 Jan 2010, 21:37
dzyubam wrote:
I'd recommend remembering the squares of integers up to 20. You'll be able to save some time if you do. If you can't tell what the multiples of a number, you'll have to find them one by one. I doubt there's some magic technique for it .
sunnyvee wrote:
bb wrote:
Explanation:
 Rating:

$$\sqrt{324} = 18$$; $$\sqrt{289} = 17$$; $$18 + 17 = 35$$

this qxn may seem dumb, but what figures did you use for $$\sqrt{289}$$?
plus cud u show shorter way of finding the multiples without having to calculate figure after figure?
hope i make sense
thank you

Memorizing squares of integers up to 20 is so worthwhile. Helped me get a quick and right answer.
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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16 Feb 2010, 07:26
lionslion wrote:
Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

to start the quiz with this question was a bummer for me, as i just simply stumped by looking at this question, wasted 90 secs to realise that the above startegy could do the job for me and was done in just over 2 mins.
it does make sense to memorize squares upto 20
but even if you don't then just check for the unit digits and should do the job
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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05 Apr 2010, 20:56
lionslion wrote:
Though i agree with dzyubam to memorize squares of numbers less than 20..

little shorter way is

for number 324

check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..

It's definitely helpful. Thanks a billion
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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07 Sep 2010, 12:24
thanks for the help!
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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09 Sep 2010, 08:31
thanks.....nice question.....
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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11 Sep 2010, 21:08
This can't be a 650 question type..

Ans is 35
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Re: GMAT Diagnostic Test Question 1 [#permalink]

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30 Jan 2011, 13:00
'check the squares of 1 digit number having units digits of 4 (2 & 8) so, answer for the above number should be either 12 or 18. If the number is little higher you need to check for 22 and 28

similarly for the number 289, it should be either 13, 17 as only squares of 3 and & result in 9 in units place..'

this does make sense surely
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Re: GMAT Diagnostic Test Question 1   [#permalink] 30 Jan 2011, 13:00

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