GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

It is currently 05 Apr 2020, 18:55

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

If m^(-1) = -1/3 then m^(-2) is equal to

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
Joined: 08 Jun 2011
Posts: 77
If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 26 Jul 2011, 11:31
1
2
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

88% (00:39) correct 12% (00:43) wrong based on 143 sessions

HideShow timer Statistics

If m^(-1) = -1/3 then m^(-2) is equal to

(A) -9
(B) -3
(C) -1/9
(D) 1/9
(E) 9

The answer is D and this is how OG12 explained it

m^-2 is (m^-1)^2 = m^-2. Therefore, we square all of -(1/3) which is = 1/9.

This is how I did it.

m^-1 = 1/m^1 Which in turn is 1/m.

This means that m^-2 = 1/m^2 .

So if 1/m = -(1/3) then 1/m^2 should be -(1/3^2) which is -(1/9). Why do I have to square the entire thing up? I am only squaring the bottom hence why would the negative sign go. Perhaps it's for the 1 and not for the 9?


OPEN DISCUSSION OF THIS QUESTION IS HERE: if-m-1-1-3-then-m-2-is-equal-to-144451.html
Senior Manager
Senior Manager
User avatar
Joined: 28 Jun 2009
Posts: 344
Location: United States (MA)
Re: If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 26 Jul 2011, 11:52
1
You made a mistake here.

Quote:
if 1/m = -(1/3) then 1/m^2 should be -(1/3^2) which is -(1/9).


You're right till
m^-2 = 1/m^2 and m^-1 = 1/m^1 = 1/m

given m^-1 = -(1/3) so, 1/m = -(1/3) solving this, m = -3
Now, m^-2 = 1/m^2 = 1/(-3)^2 = 1/9
Senior Manager
Senior Manager
User avatar
Joined: 03 Mar 2010
Posts: 323
Schools: Simon '16 (M$)
Re: If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 26 Jul 2011, 11:53
See it this way,
\(1/m = -1/3\)
\(m= -3 ( not 3)\)
\(1/m = 1/-3\)
\(1/m^2 = 1/(-3)^2\)
\(1/m^2 = 1/9\)
\(m^-^2 = 1/9.\)
_________________
My dad once said to me: Son, nothing succeeds like success.
Manager
Manager
avatar
Joined: 08 Jun 2011
Posts: 77
Re: If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 26 Jul 2011, 11:59
jamifahad wrote:
See it this way,
\(1/m = -1/3\)
\(m= -3 ( not 3)\)
\(1/m = 1/-3\)
\(1/m^2 = 1/(-3)^2\)
\(1/m^2 = 1/9\)
\(m^-^2 = 1/9.\)


So basically you assumed that m=-3 because there was a 1 in the top and 1 cannot possibly = -1 so the m had to have the negative sign, correct?
Senior Manager
Senior Manager
User avatar
Joined: 03 Mar 2010
Posts: 323
Schools: Simon '16 (M$)
Re: If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 26 Jul 2011, 12:06
Yes. But there is no assumption. It's a fact. It's math.
_________________
My dad once said to me: Son, nothing succeeds like success.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 62498
Re: If m^(-1) = -1/3 then m^(-2) is equal to  [#permalink]

Show Tags

New post 16 May 2016, 01:31
Lstadt wrote:
If m^(-1) = -1/3 then m^(-2) is equal to

(A) -9
(B) -3
(C) -1/9
(D) 1/9
(E) 9

The answer is D and this is how OG12 explained it

m^-2 is (m^-1)^2 = m^-2. Therefore, we square all of -(1/3) which is = 1/9.

This is how I did it.

m^-1 = 1/m^1 Which in turn is 1/m.

This means that m^-2 = 1/m^2 .

So if 1/m = -(1/3) then 1/m^2 should be -(1/3^2) which is -(1/9). Why do I have to square the entire thing up? I am only squaring the bottom hence why would the negative sign go. Perhaps it's for the 1 and not for the 9?


\(m^{-1} = -\frac{1}{3}\) --> \(\frac{1}{m}=-\frac{1}{3}\) --> \(m=-3\) --> \(m^{-2}=\frac{1}{m^2}=\frac{1}{9}\).

Answer: D.

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-m-1-1-3-then-m-2-is-equal-to-144451.html
_________________
GMAT Club Bot
Re: If m^(-1) = -1/3 then m^(-2) is equal to   [#permalink] 16 May 2016, 01:31
Display posts from previous: Sort by

If m^(-1) = -1/3 then m^(-2) is equal to

  Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne