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# If m is 2-digit positive integer and n is a positive integer, what is

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Math Revolution GMAT Instructor
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If m is 2-digit positive integer and n is a positive integer, what is  [#permalink]

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Updated on: 13 Oct 2016, 19:04
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55% (hard)

Question Stats:

57% (01:24) correct 43% (01:32) wrong based on 140 sessions

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If m is 2-digit positive integer and n is an integer, what is the units digit of (2^n)(m)(5^n)?
1) m=17
2) n=3

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"Only $79 for 1 month Online Course" "Free Resources-30 day online access & Diagnostic Test" "Unlimited Access to over 120 free video lessons - try it yourself" Originally posted by MathRevolution on 30 Sep 2016, 07:36. Last edited by MathRevolution on 13 Oct 2016, 19:04, edited 1 time in total. Board of Directors Status: Stepping into my 10 years long dream Joined: 18 Jul 2015 Posts: 3575 Re: If m is 2-digit positive integer and n is a positive integer, what is [#permalink] ### Show Tags 30 Sep 2016, 07:48 MathRevolution wrote: If m is 2-digit positive integer and n is a positive integer, what is the units digit of (2^n)(m)(5^n)? 1) m=17 2) n=3 $$(2^n)(m)(5^n) = (10^n)(m)$$ Now any number multiplied by 10 will always have 0 at the units place. in the expression above, what ever the value of m is, we will always get 0 at the unit place provided n <> 0. So, we need to know the value of n only. Only Statement B is sufficient. Hence B. _________________ My LinkedIn abhimahna. My GMAT Story: From V21 to V40 My MBA Journey: My 10 years long MBA Dream My Secret Hacks: Best way to use GMATClub | Importance of an Error Log! Verbal Resources: All SC Resources at one place | All CR Resources at one place GMAT Club Inbuilt Error Log Functionality - View More. New Visa Forum - Ask all your Visa Related Questions - here. New! Best Reply Functionality on GMAT Club! Find a bug in the new email templates and get rewarded with 2 weeks of GMATClub Tests for free Check our new About Us Page here. Retired Moderator Joined: 26 Nov 2012 Posts: 564 Re: If m is 2-digit positive integer and n is a positive integer, what is [#permalink] ### Show Tags 30 Sep 2016, 07:58 abhimahna wrote: MathRevolution wrote: If m is 2-digit positive integer and n is a positive integer, what is the units digit of (2^n)(m)(5^n)? 1) m=17 2) n=3 $$(2^n)(m)(5^n) = (10^n)(m)$$ Now any number multiplied by 10 will always have 0 at the units place. in the expression above, what ever the value of m is, we will always get 0 at the unit place provided n <> 0. So, we need to know the value of n only. Only Statement B is sufficient. Hence B. I doubt this question. Since we are clearly given that n is a positive integer...i.e. n can't be a 0. Since 0 is neither positive nor negative integer (the only one of this kind). Then obviously the value of n can be from 1 to infinite as per given positive integer condition..whatever the value of n is we always get 0 as the units digit irrespective of m value and n value for this case. I feel that n is a positive information shouldn't be given...then B is sufficient. Any thoughts ? Board of Directors Status: Stepping into my 10 years long dream Joined: 18 Jul 2015 Posts: 3575 Re: If m is 2-digit positive integer and n is a positive integer, what is [#permalink] ### Show Tags 30 Sep 2016, 09:02 msk0657 wrote: abhimahna wrote: MathRevolution wrote: If m is 2-digit positive integer and n is a positive integer, what is the units digit of (2^n)(m)(5^n)? 1) m=17 2) n=3 $$(2^n)(m)(5^n) = (10^n)(m)$$ Now any number multiplied by 10 will always have 0 at the units place. in the expression above, what ever the value of m is, we will always get 0 at the unit place provided n <> 0. So, we need to know the value of n only. Only Statement B is sufficient. Hence B. I doubt this question. Since we are clearly given that n is a positive integer...i.e. n can't be a 0. Since 0 is neither positive nor negative integer (the only one of this kind). Then obviously the value of n can be from 1 to infinite as per given positive integer condition..whatever the value of n is we always get 0 as the units digit irrespective of m value and n value for this case. I feel that n is a positive information shouldn't be given...then B is sufficient. Any thoughts ? Yes, correct. n should be given as non negative integer. Then only it would be B. So, the current question is not GMAT like question. MathRevolution, please recheck the question and post the corrected one. _________________ My LinkedIn abhimahna. My GMAT Story: From V21 to V40 My MBA Journey: My 10 years long MBA Dream My Secret Hacks: Best way to use GMATClub | Importance of an Error Log! Verbal Resources: All SC Resources at one place | All CR Resources at one place GMAT Club Inbuilt Error Log Functionality - View More. New Visa Forum - Ask all your Visa Related Questions - here. New! Best Reply Functionality on GMAT Club! Find a bug in the new email templates and get rewarded with 2 weeks of GMATClub Tests for free Check our new About Us Page here. Intern Joined: 17 Mar 2016 Posts: 14 Location: Singapore GPA: 3.5 WE: Business Development (Energy and Utilities) Re: If m is 2-digit positive integer and n is a positive integer, what is [#permalink] ### Show Tags 30 Sep 2016, 18:49 MathRevolution wrote: If m is 2-digit positive integer and n is a positive integer, what is the units digit of (2^n)(m)(5^n)? 1) m=17 2) n=3 Units digit will always be zero, given the conditions provided in the stem. D Math Revolution GMAT Instructor Joined: 16 Aug 2015 Posts: 8033 GMAT 1: 760 Q51 V42 GPA: 3.82 Re: If m is 2-digit positive integer and n is a positive integer, what is [#permalink] ### Show Tags 02 Oct 2016, 03:55 ==> In the original condition, you get 2 variables(m,n) and the answer is C. However, since this is an integer problem, a key question, if you apply CMT 4(A), when you solve 2), the first digit of (2^3)(m)(5^3) is always 0, so suffi. The answer is B. Answer B _________________ MathRevolution: Finish GMAT Quant Section with 10 minutes to spare The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy. "Only$79 for 1 month Online Course"
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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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Re: If m is 2-digit positive integer and n is a positive integer, what is  [#permalink]

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13 Oct 2016, 19:05
Hi all,

Sorry about the mistake and the question has been edited.
It is supposed to be n is an integer.
Thank you.
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Re: If m is 2-digit positive integer and n is a positive integer, what is  [#permalink]

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17 Oct 2016, 04:01
2
1
This question is incorrectly tagged as probability .
Abhishek009, you may want to tag this question to Remainders .
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Re: If m is 2-digit positive integer and n is a positive integer, what is  [#permalink]

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17 Oct 2016, 04:04
sandeepnb wrote:
This question is incorrectly tagged as probability .
Abhishek009, you may want to tag this question to Remainders .

Edited the tags. Thank you.
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Re: If m is 2-digit positive integer and n is a positive integer, what is  [#permalink]

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02 Jul 2019, 11:29
I think I get it, but I need some clarification:

"If m is 2-digit positive integer and n is an integer, what is the units digit of (2^n)(m)(5^n)?"

I get (2^n)(m)(5^n) = (10^n)(M)

So I get anything M * 10^n will result with a 0 in the units digit, but is "1) m = 17" insufficient because N can = a negative number, which will result in 1/10^n, so then the units digit will be 1 (17/10 = 1.7), if n = -1 or even 0 (17/100 = 0.17) if n = -2? So then two different solutions = insufficient.

1) m = 17
2) N = 3, will always be "0"
Re: If m is 2-digit positive integer and n is a positive integer, what is   [#permalink] 02 Jul 2019, 11:29
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