GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 15 Dec 2018, 19:40

### 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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• ### FREE Quant Workshop by e-GMAT!

December 16, 2018

December 16, 2018

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# Which of the following is closest to 10^180 – 10^30 ?

Author Message
TAGS:

### Hide Tags

Manager
Joined: 10 Feb 2011
Posts: 108
Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

01 Mar 2011, 09:55
7
00:00

Difficulty:

5% (low)

Question Stats:

75% (00:54) correct 25% (01:01) wrong based on 341 sessions

### HideShow timer Statistics

Which of the following is closest to $$10^{180} – 10^{30}$$ ?

A. $$10^{210}$$

B. $$10^{180}$$

C. $$10^{150}$$

D. $$10^{90}$$

E. $$10^6$$
Manager
Joined: 14 Feb 2011
Posts: 175
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

01 Mar 2011, 09:58
you can rewrite it as $$10^30$$*($$10^150$$ - 1). Now $$10^150$$ - 1 is ~$$10^150$$ so expression is closest to 10^180.

Math Expert
Joined: 02 Sep 2009
Posts: 51218
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

01 Mar 2011, 10:10
banksy wrote:
Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6

10^180 is much, much, much bigger number than 10^30 and as we need approximate value then it's pretty much negligible in this case, so: 10^180 – 10^30=~10^180.

_________________
Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 8678
Location: Pune, India
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

01 Mar 2011, 16:55
2
banksy wrote:
Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6

If you have difficulty in visualizing this approximation, think about it this way:

Which of the following is closest to 10^2 – 10^1 ?

A. 1
B. 10
C. 100
D. 1000

100 - 10 is 90. Since, for a reasonably big number, a smaller power of the number is much smaller than any greater power, the answer will definitely be closer to 10^180 than any other power of 10.
_________________

Karishma
Veritas Prep GMAT Instructor

Manager
Joined: 12 Jan 2013
Posts: 153
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

28 Dec 2013, 04:34
banksy wrote:
Which of the following is closest to 10^180 – 10^30 ?

A. 10^210
B. 10^180
C. 10^150
D. 10^90
E. 10^6

10^180 - 10^30 can be written as 10^30*(10^150 - 1) just as the first poster said, but one other thing is worth mentioning: PEMDAS.

When you both have multiplication and parenthesis, do the operation in the parenthesis first, then the multiplication. In our case, the subtraction is extremely minescule and thus the parenthesis is almost exactly 10^150.

Now, do the multiplication: 10^30 * 10^150 = 10^180
Moderator
Joined: 21 Jun 2014
Posts: 1098
Location: India
Concentration: General Management, Technology
GMAT 1: 540 Q45 V20
GPA: 2.49
WE: Information Technology (Computer Software)
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

18 Jun 2016, 10:21
10^180 – 10^30

10^30 * (10^150 – 1)

as we know 10^2 - 1 means 100-1 and we get 99, which is approximately 100. hence (10^150 – 1) would remain as 10^150.
and 10^30 * 10^150 = 10^180. Answer is B.
_________________

---------------------------------------------------------------
Target - 720-740
Project PS Butler - https://gmatclub.com/forum/project-ps-butler-practice-everyday-280904.html
http://gmatclub.com/forum/information-on-new-gmat-esr-report-beta-221111.html
http://gmatclub.com/forum/list-of-one-year-full-time-mba-programs-222103.html

VP
Status: Learning
Joined: 20 Dec 2015
Posts: 1066
Location: India
Concentration: Operations, Marketing
GMAT 1: 670 Q48 V36
GRE 1: Q157 V157
GPA: 3.4
WE: Engineering (Manufacturing)
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

24 Jun 2017, 08:19
This is a good question for approximation .
10^180 is much greater than 10^30
_________________

Non-Human User
Joined: 09 Sep 2013
Posts: 9172
Re: Which of the following is closest to 10^180 – 10^30 ?  [#permalink]

### Show Tags

16 Jul 2018, 20:48
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: Which of the following is closest to 10^180 – 10^30 ? &nbs [#permalink] 16 Jul 2018, 20:48
Display posts from previous: Sort by