It is currently 18 Mar 2018, 20:19

### 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

# What is 157609^(1/2)?

Author Message
TAGS:

### Hide Tags

Senior SC Moderator
Joined: 14 Nov 2016
Posts: 1282
Location: Malaysia

### Show Tags

13 Jan 2017, 22:34
1
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

61% (00:57) correct 39% (00:36) wrong based on 122 sessions

### HideShow timer Statistics

What is $$\sqrt{157609}$$?

(A) 323
(B) 378
(C) 392
(D) 397
(E) 403
[Reveal] Spoiler: OA

_________________

"Be challenged at EVERY MOMENT."

“Strength doesn’t come from what you can do. It comes from overcoming the things you once thought you couldn’t.”

"Each stage of the journey is crucial to attaining new heights of knowledge."

Last edited by hazelnut on 20 Jan 2017, 07:50, edited 2 times in total.
Manager
Joined: 25 Jun 2016
Posts: 61
GMAT 1: 780 Q51 V46

### Show Tags

13 Jan 2017, 23:01
One way to attack this problem is to consider squaring the answer choices. When squared, the right answer will be 157609. We want to minimize calculation, so we want to look for shortcuts.

First, if the square of a number ends in 9 then the number itself will end in 3 or 7. So B and C are gone. We could have also noticed that both B and C are even, so their squares will also be even.

E, 403, is pretty close to a number that's easy to work with, 400, so let's consider E next. 400^2 = 160000, so 403^2 will be bigger still. Our number is smaller, so E is gone.

If we start multiplying A, 323, out the long way we find that the tens digit is 2, not 0. Eliminate.

D is all that's left.
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3353
Location: India
GPA: 3.5

### Show Tags

14 Jan 2017, 00:07
1
This post was
BOOKMARKED
ziyuenlau wrote:
What is $$\sqrt{157609}$$?

(A) 323
(B) 378
(C) 392
(D) 397
(E) 403

$$300^2 = 9000$$
$$400^2 = 16000$$
$$350^2 = 122500$$

So, The number must be Greater than 350 and the units digit of the number must end in 3 and 7...

Among the given options only (D) fits in perfectly , hence, correct answer must be (D)

_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Intern
Joined: 09 Jan 2017
Posts: 6

### Show Tags

14 Jan 2017, 00:41
157609 is odd so its sq rt cannot be even. Eliminate B,C

Option E is 403, 400 is sq rt of 160000 which is greater than 157609. We are left with 323 and 397. Now 350 square is 122500 so 323 can be eliminated. Hence answer is d 397

Sent from my ASUS_Z010D using GMAT Club Forum mobile app
Intern
Joined: 28 Aug 2016
Posts: 16

### Show Tags

19 Nov 2017, 07:34
Since the units digit has to be 9 so only 323 and 397 will remain, then we can take a square of 320 and determine that 323 will not be our answer coz 320^2= 102400 so therefore D is our answer
BSchool Forum Moderator
Joined: 26 Feb 2016
Posts: 2263
Location: India
GPA: 3.12

### Show Tags

19 Nov 2017, 09:08
hazelnut wrote:
What is $$\sqrt{157609}$$?

(A) 323
(B) 378
(C) 392
(D) 397
(E) 403

$$400^2 = 160000$$
Also, for the last digit 9, the square root could be 3 or 7 because $$\sqrt{49} = 7$$ and $$\sqrt{9} = 3$$
Since the number in question is slightly below 160000, the square root cannot be 403.

Therefore, the number must be 397(Option D)

Another method to tests our answer is $$(397)^2 = (400 - 3)^2 = 160000 + 9 - 2(400)(3) = 160009 - 2400 = 157609$$
_________________

Stay hungry, Stay foolish

Re: What is 157609^(1/2)?   [#permalink] 19 Nov 2017, 09:08
Display posts from previous: Sort by