Last visit was: 19 Nov 2025, 05:02 It is currently 19 Nov 2025, 05:02
Home
GMAT
Messages
Tests
Schools
Events
Rewards
Chat
My Profile
Close
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
Your Progress

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
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
505-555 Level|   Exponents|      
User avatar
gmatjon
User avatar
Joined: 18 Aug 2009
Last visit: 21 Jul 2013
Posts: 216
Own Kudos:
360
 [18]
Given Kudos: 16
Concentration: Accounting
Schools:UT at Austin, Indiana State University, UC at Berkeley
GPA: 3.8
WE 1: 5.5
WE 2: 5.5
WE 3: 6.0
GMAT 1: 700 Q49 V36
Posts: 216
Kudos: 360
 [18]
10^180-10^30. Which of the following best approximates 24 Sep 2009, 10:08
3
Kudos
Add Kudos
15
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

15% (low)

Question Stats:

73% (00:46) correct 27% (01:14) wrong based on 421 sessions

History

Date
Time
Result
Not Attempted Yet
10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

(A) 10^180
(B) 10^179
(C) 10^170
(D) 10^160
(E) 10^150
ShowHide Answer
Official Answer
A
User avatar
AKProdigy87
User avatar
Joined: 11 Sep 2009
Last visit: 11 Mar 2015
Posts: 80
Own Kudos:
1,128
 [4]
Given Kudos: 6
Posts: 80
Kudos: 1,128
 [4]
10^180-10^30. Which of the following best approximates 24 Sep 2009, 11:03
2
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
The answer is A: 10^180.

10^180 - 10^30
= 10^30 (10^150 - 1)
~ 10 ^30 (10^150)
~ 10^180

This is more about the relative scale of the quantities than anything. It's easier to think about it with numbers you can picture, so assume you have an equation like 1 000 000 000 (10^7) - 100 (10^2). This equation can still be approximated as 10^7, since the latter term is so insignificantly small compared to the former term.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 19 Nov 2025
Posts: 105,385
Own Kudos:
778,202
Given Kudos: 99,977
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,385
Kudos: 778,202
10^180-10^30. Which of the following best approximates 17 Jan 2012, 15:27
Kudos
Add Kudos
Bookmarks
Bookmark this Post
10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

(A) 10^180
(B) 10^179
(C) 10^170
(D) 10^160
(E) 10^150

10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

Yes, answer 10^180 is correct. Note that we need approximate value of the given expression and as 10^(180) is much larger number than 10^(30) then 10^(30) is pretty much negligible in this case: 10^(180)-10^(30)=~10^(180).

Check similar question for practice: https://gmatclub.com/forum/tough-and-tri ... l#p1029229

Hope it helps.
User avatar
cumulonimbus
User avatar
Joined: 14 Nov 2011
Last visit: 10 Feb 2023
Posts: 97
Own Kudos:
62
Given Kudos: 102
Location: United States
Concentration: General Management, Entrepreneurship
GPA: 3.61
WE:Consulting (Manufacturing)
Posts: 97
Kudos: 62
10^180-10^30. Which of the following best approximates 08 Jul 2013, 18:25
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
Baten80
I found the answer options are:
a. 10^210
b. 10^180
c. 10^150
d. 10^90
e. 10^6

I answered B.
What is correct?

10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

Yes, answer 10^180 is correct. Note that we need approximate value of the given expression and as 10^(180) is much larger number than 10^(30) then 10^(30) is pretty much negligible in this case: 10^(180)-10^(30)=~10^(180).

Check similar question for practice: tough-and-tricky-exponents-and-roots-questions-125956-40.html#p1029229

Hope it helps.
Show more

Hi Bunnel,
Their are two sets of options on this page.
How to decide b/w 10^180 and 10^179.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 19 Nov 2025
Posts: 105,385
Own Kudos:
778,202
 [4]
Given Kudos: 99,977
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,385
Kudos: 778,202
 [4]
10^180-10^30. Which of the following best approximates 08 Jul 2013, 23:09
3
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
cumulonimbus
Bunuel
Baten80
I found the answer options are:
a. 10^210
b. 10^180
c. 10^150
d. 10^90
e. 10^6

I answered B.
What is correct?

10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

Yes, answer 10^180 is correct. Note that we need approximate value of the given expression and as 10^(180) is much larger number than 10^(30) then 10^(30) is pretty much negligible in this case: 10^(180)-10^(30)=~10^(180).

Check similar question for practice: tough-and-tricky-exponents-and-roots-questions-125956-40.html#p1029229

Hope it helps.

Hi Bunnel,
Their are two sets of options on this page.
How to decide b/w 10^180 and 10^179.
Show more

Still 10^180 would be correct.

To illustrate: \(10^{180}-10^{30}=10^{30}(10^{150}-1)\).

Now, \(10^{150}-1\) is VERY close to \(10^{150}\), thus \(10^{30}(10^{150}-1)\approx{10^{30}10^{150}=10^{180}}\).

Similar questions to practice:
the-value-of-10-8-10-2-10-7-10-3-is-closest-to-which-of-95082.html
which-of-the-following-is-closest-to-10180-1030-a-110224.html
which-of-the-following-best-approximates-the-value-of-q-if-99674.html
new-tough-and-tricky-exponents-and-roots-questions-125956-40.html
if-x-10-10-x-2-2x-7-3x-2-10x-2-is-closest-to-143897.html
1-0-0001-0-04-10-the-value-of-the-expression-above-is-59398.html
m24-q-7-explanation-76513.html

Hope it helps.
User avatar
pqhai
User avatar
Retired Moderator
Joined: 16 Jun 2012
Last visit: 26 Nov 2015
Posts: 867
Own Kudos:
8,883
Given Kudos: 123
Location: United States
Posts: 867
Kudos: 8,883
10^180-10^30. Which of the following best approximates 09 Jul 2013, 00:27
Kudos
Add Kudos
Bookmarks
Bookmark this Post
cumulonimbus
Bunuel
Baten80
I found the answer options are:
a. 10^210
b. 10^180
c. 10^150
d. 10^90
e. 10^6

I answered B.
What is correct?

10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

Yes, answer 10^180 is correct. Note that we need approximate value of the given expression and as 10^(180) is much larger number than 10^(30) then 10^(30) is pretty much negligible in this case: 10^(180)-10^(30)=~10^(180).

Check similar question for practice: tough-and-tricky-exponents-and-roots-questions-125956-40.html#p1029229

Hope it helps.

Hi Bunnel,
Their are two sets of options on this page.
How to decide b/w 10^180 and 10^179.
Show more

Hi cumulonimbus

I think 10^180 is closer. Because 1 is very small, 10^x - 1 is closer to 10^x than 10^(x-1).

Let try few examples, you can see the pattern.
10^2 - 1= 99 ==> closer to 10^2 = 100 than 10^1 = 10
10^3 - 1 = 999 ==> closer to 10^3 = 1000 than 10^2 = 100
10^4 - 1 = 9999 ===> closer to 10^4 = 10000 than 10^3 = 1000
.....
10^180 - 1 ==> closer to 10^180 than 10^179

Hope it helps.
avatar
PareshGmat
avatar
Joined: 27 Dec 2012
Last visit: 10 Jul 2016
Posts: 1,534
Own Kudos:
8,100
Given Kudos: 193
Status:The Best Or Nothing
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Posts: 1,534
Kudos: 8,100
10^180-10^30. Which of the following best approximates 26 Feb 2014, 23:01
Kudos
Add Kudos
Bookmarks
Bookmark this Post
10^180 is way too higher than 10^30,
10^180 is the Answer = A
User avatar
stonecold
User avatar
Joined: 12 Aug 2015
Last visit: 09 Apr 2024
Posts: 2,244
Own Kudos:
3,549
Given Kudos: 893
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Schools: Boston U '20 (M)
GRE 1: Q169 V154
Posts: 2,244
Kudos: 3,549
10^180-10^30. Which of the following best approximates 29 Nov 2016, 14:13
Kudos
Add Kudos
Bookmarks
Bookmark this Post
gmatjon
10^180 - 10^30 =
Which of the following best approximates the value of the expression above?

(A) 10^180
(B) 10^179
(C) 10^170
(D) 10^160
(E) 10^150
Show more

Nice Question this one.
This is how i solved this one up
I didn't realise that 10^30 was negligible straight away

10^30 can be factored out here.
10^30(10^150 - 1)
Now 1 is definitely negligible w.r.t 10^150
Hence expression reduced to 10^30*10^150 => 10^180

Hence A
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,583
Own Kudos:
1,079
Posts: 38,583
Kudos: 1,079
10^180-10^30. Which of the following best approximates 20 Jun 2024, 22:20
Kudos
Add Kudos
Bookmarks
Bookmark this Post
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.
Moderators:
Bunuel
Math Expert
105383 posts
Krunaal
Tuck School Moderator
805 posts