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.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: If # represents one of the operations +,- and *, is a # [#permalink]
19 Sep 2010, 23:14

Expert's post

BalakumaranP wrote:

IMO, it cannot be "not equal" always.

If # is subtraction,

a#(b-c)=a-(b-c)=a-b+c

(a#b)-(a#c)=(a-b)-(a-c)=a-b-a+c=-b+c

a-b+c=-b+c when a=0 and not equal for other values.. So both are insufficient.. Am I missing something here?

If # represents one of the operations +, - and *, is a#(b-c)=(a#b)-(a#c)for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a.

# is neither addition (as a+1=1+a) not multiplication (as a*1=1*a), so # is a subtraction. Then LHS=a#(b-c)=a-b+c and RHS=(a#b)-(a#c)=(a-b)-(a-c)=c-b, so the question becomes "is a-b+c=c-bfor all numbers a, b and c?" --> "is a=0". So when a=0 (and # is a subtraction) then a#(b-c)=(a#b)-(a#c) holds true but not for other values of a, so not for all numbers a, b and c. Answer to the question is NO. Sufficient.

(2) # represents subtraction --> the same as above. Sufficient.

Re: If # represents one of the operations +,- and *, is a # [#permalink]
21 Sep 2010, 09:55

zisis wrote:

If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction

Mods, please to DS section...posted by mistake in PS - apologies

You're told that "#" is either addition, subtraction, or multiplication, and then asked if "#" satisfies the distributive property. Of these three, distribution only holds for multiplication, so if "#" is "*", it holds, and if "#" isn't "*", then it does not hold.

All we really need to know is what operation "#" really is.

(1) This is only true of subtraction, so # is subtraction and the distributive property does not hold. Sufficient. (2) Same as above. Sufficient.

(D)

gmatclubot

Re: If # represents one of the operations +,- and *, is a #
[#permalink]
21 Sep 2010, 09:55

I couldn’t help myself but stay impressed. young leader who can now basically speak Chinese and handle things alone (I’m Korean Canadian by the way, so...