It is currently 19 Jun 2019, 22:57

### 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

# QOTD#17 Which of the following is closest to

Author Message
TAGS:
GRE Prep Club Legend
Joined: 07 Jun 2014
Posts: 4810
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 118

Kudos [?]: 1899 [0], given: 397

QOTD#17 Which of the following is closest to [#permalink]  12 Sep 2016, 11:58
Expert's post
00:00

Question Stats:

48% (01:15) correct 52% (00:39) wrong based on 25 sessions
Which of the following is closest to $$\sqrt{(2.3)(10^9)}$$?

A. 50,000
B. 150,000
C. 500,000
D. 1,500,000
E. 5,000,000

Practice Questions
Question: 16
Page: 206
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

GRE Instructor
Joined: 10 Apr 2015
Posts: 1991
Followers: 60

Kudos [?]: 1806 [1] , given: 9

Re: QOTD#17 Which of the following is closest to [#permalink]  19 Sep 2016, 17:11
1
KUDOS
Expert's post
Explanation

Always scan the answer choices BEFORE performing any calculations.
Since the answer choice are very spread apart, we can be very aggressive with our estimation.

We're going to use a nice rule that says √(ab) = (√a)(√b)

We have √(2.3 x 10⁹)
Since 2.3 isn't an easy number to find the square root of, the above rule doesn't help us much.
However, what if we do the following:
√(2.3 x 10⁹) = √(2.3 x 10¹ x 10⁸)
= √(23 x 10⁸)

How does this help?
Well, 23 is pretty close to 25 and we know that √25 = 5.
Can we do this? You bet. Remember that since the answer choice are very spread apart, we can be very aggressive with our estimation

We get:
√(23 x 10⁸) = (√23)(√10⁸)
≈ 5(10⁴)
≈ 5(10,000)
≈ 50,000

Cheers,
Brent
_________________

Brent Hanneson – Creator of greenlighttestprep.com

Intern
Joined: 26 Jul 2017
Posts: 1
Followers: 0

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

Re: QOTD#17 Which of the following is closest to [#permalink]  11 Aug 2017, 10:38
well i did it differently,
i checked the answers and i squared the first and divided it by 2.3 and fount out that it's the closest to 10^9, all the other are just way off
though i guess it may not work as well
Manager
Joined: 26 Jun 2017
Posts: 104
Followers: 0

Kudos [?]: 41 [0], given: 38

Re: QOTD#17 Which of the following is closest to [#permalink]  21 Aug 2017, 09:29
If we have a problem 10^4, is not the solution 100,000? Since the decimal point is in the end of 10. so we carry the point 4 step right.
_________________

What you think, you become.

Re: QOTD#17 Which of the following is closest to   [#permalink] 21 Aug 2017, 09:29
Display posts from previous: Sort by