Last visit was: 14 Jun 2024, 02:53 It is currently 14 Jun 2024, 02:53
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.
Close
Request Expert Reply
Confirm Cancel
SORT BY:
Date
Tags:
Show Tags
Hide Tags
User avatar
Intern
Intern
Joined: 05 Dec 2011
Posts: 10
Own Kudos [?]: 203 [8]
Given Kudos: 11
WE:Information Technology (Computer Software)
Send PM
User avatar
Intern
Intern
Joined: 10 Feb 2012
Posts: 33
Own Kudos [?]: 333 [4]
Given Kudos: 41
Location: India
Concentration: Marketing, Strategy
GMAT 1: 640 Q48 V31
GPA: 3.45
WE:Marketing (Pharmaceuticals and Biotech)
Send PM
Math Expert
Joined: 02 Sep 2009
Posts: 93707
Own Kudos [?]: 631616 [0]
Given Kudos: 82302
Send PM
avatar
SVP
SVP
Joined: 27 Dec 2012
Status:The Best Or Nothing
Posts: 1559
Own Kudos [?]: 7264 [0]
Given Kudos: 193
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
domu904 wrote:
What is the value of 10^8 - 6^7?

A. 99,720,064
B. 99,720,069
C. 99,721,022
D. 99,722,055
E. 99,723,097


\(10^8\) ends with 0; \(6^7\) ends with 6

Difference will provide 4 at the units place

Answer = A
Director
Director
Joined: 12 Nov 2016
Posts: 569
Own Kudos [?]: 118 [0]
Given Kudos: 167
Location: United States
Schools: Yale '18
GMAT 1: 650 Q43 V37
GRE 1: Q157 V158
GPA: 2.66
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
domu904 wrote:
What is the value of 10^8 - 6^7?

A. 99,720,064
B. 99,720,069
C. 99,721,022
D. 99,722,055
E. 99,723,097


We can attack this question a bit differently using some properties

Rule 1

10^n power = 1 with n amount of zeros... 10^2 is 100 (2 zero) 10^5 100,000 (five zero)

so

100000000 -6^7

Rule 2

What is unit digits of 6? 6 is a special number 6^n will always have a units digit of 6 so the units digits of the answer must be 4

Thus
"A"
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6065
Own Kudos [?]: 4738 [0]
Given Kudos: 463
Location: India
GPA: 3.5
WE:Business Development (Commercial Banking)
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
domu904 wrote:
What is the value of 10^8 - 6^7?

A. 99,720,064
B. 99,720,069
C. 99,721,022
D. 99,722,055
E. 99,723,097


\(10^8\) Will have units digit as 0
\(6^7\) Will have units digit as 6

Now, \(10^8 - 6^7\) will have units digit as \(0 - 6 = 4\)

Among the given options only (A) satisfies, so that is the answer...
Target Test Prep Representative
Joined: 04 Mar 2011
Status:Head GMAT Instructor
Affiliations: Target Test Prep
Posts: 3042
Own Kudos [?]: 6449 [0]
Given Kudos: 1646
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
Expert Reply
domu904 wrote:
What is the value of 10^8 - 6^7?

A. 99,720,064
B. 99,720,069
C. 99,721,022
D. 99,722,055
E. 99,723,097


Since we know that the GMAT would not expect us to carry out the computation of the exact value of 10^8 - 6^7, we can focus on the units digits of the resulting difference.

When we raise 10 to any power, the units digit of the answer is always 0. For example, 10^2 = 100 and 10^4 = 10,000. Similarly, the units digit of 6 raised to any power is 6. For example, 6^2 = 36, 6^3 = 216, etc.
In this problem, the units digit of 10^8 will be 0 and the units digit of 6^7 will be 6. Thus, subtracting 6 from 10 (after 0 “borrows” a 1 from the tens digit) will result in a units digit of 4. Therefore, 10^8 - 6^7 must be equal to 99,720,064 since that is the only answer choice with a units digit of 4.

Answer: A
Manager
Manager
Joined: 18 Jun 2018
Posts: 222
Own Kudos [?]: 425 [0]
Given Kudos: 35
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
domu904 wrote:
What is the value of 10^8 - 6^7?

A. 99,720,064
B. 99,720,069
C. 99,721,022
D. 99,722,055
E. 99,723,097


OA:A

Unit digit of \(10^8\) is \(0\) and unit digit of \(6^7\) is \(6\), Unit digit of expression \(10^8 - 6^7\) will be \(10-6 = 4\), as \(10^8>6^7\).
Only Option A has 4 at unit's digit.
User avatar
Non-Human User
Joined: 09 Sep 2013
Posts: 33549
Own Kudos [?]: 837 [0]
Given Kudos: 0
Send PM
Re: What is the value of 10^8 - 6^7? [#permalink]
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.
GMAT Club Bot
Re: What is the value of 10^8 - 6^7? [#permalink]
Moderator:
Math Expert
93707 posts