If ab = ac is b = 2 ? : Retired Discussions [Locked]
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 10 Dec 2016, 23:45

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If ab = ac is b = 2 ?

Author Message
Manager
Joined: 14 Dec 2011
Posts: 70
Followers: 0

Kudos [?]: 51 [0], given: 69

If ab = ac is b = 2 ? [#permalink]

### Show Tags

16 Jan 2013, 07:57
1
This post was
BOOKMARKED
If ab = ac is b = 2 ?

(1) c = 1
(2) a is a prime number and c is NOT a prime number

I got this step correct $$a(b-c)=0$$ : either $$a=0$$ or $$b=c$$

But (1), i selected this one as the answer along with (2)
Not sure why this isn't correct. My understanding says b = 1 because b = c, which is 1.
Not able to understand (1)'s explanation:- $$c=1$$ . If $$a=0$$ then $$b$$ can take any value irrespective of the value of $$c$$ . Not sufficient.

Thanks & Regards
Vinni
Math Expert
Joined: 02 Sep 2009
Posts: 35951
Followers: 6867

Kudos [?]: 90128 [1] , given: 10418

Re: If ab = ac is b = 2 ? [#permalink]

### Show Tags

16 Jan 2013, 09:01
1
KUDOS
Expert's post
vinnik wrote:
If ab = ac is b = 2 ?

(1) c = 1
(2) a is a prime number and c is NOT a prime number

I got this step correct $$a(b-c)=0$$ : either $$a=0$$ or $$b=c$$

But (1), i selected this one as the answer along with (2)
Not sure why this isn't correct. My understanding says b = 1 because b = c, which is 1.
Not able to understand (1)'s explanation:- $$c=1$$ . If $$a=0$$ then $$b$$ can take any value irrespective of the value of $$c$$ . Not sufficient.

Thanks & Regards
Vinni

OFFICIAL SOLUTION:
If $$ab=ac$$ is $$b=2$$?

Notice that we cannot reduce $$ab=ac$$ by $$a$$ and write $$b=c$$, since $$a$$ can be zero and division by zero is not allowed. $$ab=ac$$ --> $$a(b-c)=0$$ --> either $$a=0$$ or $$b=c$$.

(1) $$c=1$$ --> if $$a=0$$ then $$b$$ can tale any value irrespective of the value of $$c$$. Not sufficient.

(2) $$a$$ is a prime number and $$c$$ is NOT a prime number --> $$a=prime$$ means that $$a\neq{0}$$, so it must be true that $$b=c$$. Now, since also given that $$c\neq{prime}$$ then $$b$$ is also not equal to a prime number so it cannot equal to a prime number 2. Sufficient.

As for your question. We have that either a=0 OR b=c.

Now, if for (1) a=0, then b can take ANY value. Consider a=0, c=1 and b=(any value) --> ab=ac=0.

Hope it's clear.
_________________
Manager
Joined: 14 Dec 2011
Posts: 70
Followers: 0

Kudos [?]: 51 [0], given: 69

Re: If ab = ac is b = 2 ? [#permalink]

### Show Tags

16 Jan 2013, 09:45
Bunuel wrote:
As for your question. We have that either a=0 OR b=c.

Now, if for (1) a=0, then b can take ANY value. Consider a=0, c=1 and b=(any value) --> ab=ac=0.

Hope it's clear.

ab = ac
0 * b = 0 * 1

got it. Thank you.

Regards
Vinni
Re: If ab = ac is b = 2 ?   [#permalink] 16 Jan 2013, 09:45
Similar topics Replies Last post
Similar
Topics:
M24-12-Do graphs y=ax2+b a 1 14 May 2013, 21:22
A regular pentagon is inscribed in a circle. If A and B are 0 25 Dec 2012, 08:29
2 M01-36: Is the product of a and b equal to 1? 5 09 Jun 2012, 07:49
1 M14, 33 (If ab≠0 and |a|<|b|, which of the following must) 10 09 Jun 2012, 07:10
1 Event A and Event B are independent. Is the probability that 6 23 Oct 2007, 07:13
Display posts from previous: Sort by

# If ab = ac is b = 2 ?

Moderator: Bunuel

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.