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## If m^(-1) = -1/3 (OG16)

tagged by: Brent@GMATPrepNow

# Forum: If m^(-1) = -1/3 (OG16)

00:00

A

B

C

D

E

## Global Stats

Difficult

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

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

OA: D

### GMAT/MBA Expert

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boomgoesthegmat wrote:
If m^(-1) = -1/3, then m^(-2) is equal to

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

OA: D
m^(-1) = 1/m

We're told that m^(-1) = -1/3
This means that 1/m = -1/3
So, we know that m = -3

This means that m^(-2) = (-3)^(-2)
= 1/9
= D

RELATED RESOURCE (video):
Negative exponents: https://www.gmatprepnow.com/module/gmat-powers-and-roots/video/1028

Cheers,
Brent

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### GMAT/MBA Expert

GMAT Instructor
Joined
08 Dec 2008
Posted:
12128 messages
Followed by:
1237 members
5254
GMAT Score:
770
boomgoesthegmat wrote:
If m^(-1) = -1/3, then m^(-2) is equal to

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

OA: D
Another solution:
Given: m^(-1) = -1/3
Square both sides to get: [m^(-1)]^2 = (-1/3)^2
Simplify: m^(-2) = (-1/3)(-1/3)
So, m^(-2) = 1/9

RELATED RESOURCE (video)
- Laws of exponents - part I: https://www.gmatprepnow.com/module/gmat-powers-and-roots/video/1025

Cheers,
Brent

_________________
Brent Hanneson – Creator of GMATPrepNow.com
Use our video course along with

And check out all of our free resources

GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months!

### GMAT/MBA Expert

GMAT Instructor
Joined
09 Apr 2015
Posted:
1461 messages
Followed by:
16 members
39
boomgoesthegmat wrote:
If m^(-1) = -1/3, then m^(-2) is equal to

A) -9
B) -3
C) -1/9
D) 1/9
E) 9
Notice that m^(-2) = [m^(-1)]^2, therefore,

m^(-2) = (-1/3)^2 = 1/9

Alternate Solution:

We re-express m^(-1) as 1/m. We are given that m^(-1) = -1/3, so we see that m = -3.

To evaluate m^(-2), we substitute -3 for m, yielding (-3)^(-2) = 1/(-3)^2 = 1/9.

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Jeffrey Miller Head of GMAT Instruction

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