Author 
Message 
TAGS:

Hide Tags

Retired Moderator
Joined: 27 Oct 2017
Posts: 1273
Location: India
Concentration: International Business, General Management
GPA: 3.64
WE: Business Development (Energy and Utilities)

For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
Updated on: 07 Oct 2018, 06:39
Question Stats:
18% (02:11) correct 82% (02:34) wrong based on 62 sessions
HideShow timer Statistics
For positive integers n and m (n>m), is the average (arithmetic mean) of 4(10^n), 4(10^(n1)), ......, and 4(10^(nm)) an integer? 1) m<6 2) n=10 Weekly Quant Quiz #3 Question No 8
Official Answer and Stats are available only to registered users. Register/ Login.
_________________
Originally posted by gmatbusters on 06 Oct 2018, 10:34.
Last edited by gmatbusters on 07 Oct 2018, 06:39, edited 2 times in total.
Renamed the topic and edited the question.




Senior PS Moderator
Status: It always seems impossible until it's done.
Joined: 16 Sep 2016
Posts: 732
GMAT 1: 740 Q50 V40 GMAT 2: 770 Q51 V42

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:53
The answer should be A. Please find soln attached. BEst, G
Attachments
Q8.jpeg [ 115.9 KiB  Viewed 745 times ]
_________________
Regards, Gladi
“Do. Or do not. There is no try.”  Yoda (The Empire Strikes Back)




Intern
Joined: 16 Aug 2018
Posts: 2

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:43
E.
No information is given about n in Statement 1. No information is given about m in Statement 2. Combining the statements, it can be determined that the sum of all entries amount to an integer but because we don't know if there is an odd or even number of entries and, thus, if sum of all entries divided by the number of entries will be an integer or not.



Manager
Joined: 16 Sep 2011
Posts: 101

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:46
For positive integers n and m (n>m), is the average (arithmetic mean) of 4(10^n), 4(10^(n1)), ......, and 4(10^(nm)) an integer?
1) m<6 2) n=10
av= 4 (10^n +10^n1 + 10 ^ n2 +......10^(nm)/(m+1)
= (4 *10^(n) (1+1/10 +1/10^2 +.....+1/10^m))/(m+1)
= (4* 10^n * (1* (1/10)^m1  1)/ (11/10). )/(m+1)
so if m<6 we cant say for m+1 in denominator as if m=2 m+1 becomes 3 ... hence not sufficient Option B is not required
E is the answer



Intern
Joined: 02 Apr 2018
Posts: 48

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:50
E. statment 1 is not sufficient. if we know m is less than 6 then we could have at least 6 terms in total. but we know that the numerator will not be divisible by 6. however if m is 3 then we have 4 terms and the numerator is divisible by 4
statment 2 is not sufficient because it doesnt say anything about m
both these statments won't solve the question because we dont know what m is



Intern
Joined: 06 Feb 2018
Posts: 16

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:57
St 1 suggests m<6
Since m will be in the denominator (m decides the number of factors) if we want to calculate the average, if we have m has 5 or 4 or 3 or 2, we have numerator as 4x10^nm(1 + 10 + .... + 10^m) which are divisible by those numbers regardless of the value of n (as long as n>m)
Sufficient
St 2 gives us a value of n. But no value of m is specified (m = 1,2....11) which means when we have m in the denominator, we are not sure if it divides numerator or not)
Insufficient
A



Manager
Joined: 21 Jul 2017
Posts: 186
Location: India
Concentration: Social Entrepreneurship, Leadership
GPA: 4
WE: Project Management (Education)

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 10:57
Correct answer is A
Attachments
Screen Shot 20181006 at 11.26.58 PM.png [ 245.94 KiB  Viewed 731 times ]



RC Moderator
Joined: 24 Aug 2016
Posts: 782
GMAT 1: 540 Q49 V16 GMAT 2: 680 Q49 V33

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
06 Oct 2018, 11:18
avg of 4(10^n), 4(10^(n1)), ......, and 4(10^(nm)) is integer when nm=1, 2, 3 ,4, 5 ,7,8,10......etc but not for 6 & as 1111111/7 gives a non terminating number. 1) not suff..... no info about n and there could or could not be a possibility of nm EQ & NE 6 2)not suff..... no info about M and there could or could not be a possibility of nm EQ & NE 6 1+2) not suff........ as there could or could not be a possibility of nm EQ & NE 6 AnS E
_________________
Please let me know if I am going in wrong direction. Thanks in appreciation.



Intern
Joined: 14 Aug 2017
Posts: 43
Location: India
Concentration: Other, General Management

Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
Show Tags
13 Sep 2019, 03:49
gmatbusters wrote: For positive integers n and m (n>m), is the average (arithmetic mean) of 4(10^n), 4(10^(n1)), ......, and 4(10^(nm)) an integer? 1) m<6 2) n=10 Weekly Quant Quiz #3 Question No 8 the answwer is defincaty A , easy loigic is AMean is integer for all odd numbers, so we need to worry for 2,4 ( values of m). for a series with 2 or 4 values that are multiple of 4 . the AM is always an integer. gmatbuster any views




Re: For positive integers n and m (n>m), is the average (arithmetic mean)
[#permalink]
13 Sep 2019, 03:49






