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:

A clarification required from STOLYAR [#permalink]
03 Oct 2003, 22:59

Hi stolyar
I needed some clarification on one of the questions u had put in the excel tool created by this site. Its on probability. It said that there are 6 commodities A B C D E F and we have to choose 3 . E has already been choosen and what is the probability of choosing in the remaining 2.

My solution. as E has already been chosen 2 commodities can be choosen out of 5 in 2C5 ways = 10 ways.
Also B can choosen in 4 different ways. BA, BC , BD, BF so the probability is 4/10 =.4

Your solution P(E^B) = 1/30 (1/5*1/5)
P(E)= 1/6
therefore P(B)= P(E^B) / P(E) = .2
Fair enuf I would say. But why isnt the same answer coming from my method. Probably am missing out something. I wpould appreciate ur comment.

this question is not mine, so I need some clarification:

Your verbiage says: there are 6 commodities A B C D E F and we have to choose 3 . E has already been choosen and what is the probability of choosing (WHAT? ANY?) in the remaining 2.

sorry stolyar... I just missed "B" in my last sentence. E has already been chosen and we need to chose 2 more from the remaining 5 . so what is the probablility that one of them would be B. And the excel had ur name above the question so I presumed it was urs.
thanks for ur prompt reply
neeraj

the verbiage is slightly ambiguous. there should be words: provided that E is already taken. This would be a question about conditional probability: to find P of smth if smth else has already happened.

P(E B any)=P(E)*P(B any/E)
P(B any/E)=P(E B any)/P(E)
P(E B any)=1/6*1/5*4/4=1/30
P(E)=1/6

P=1/30:1/6=1/5=0.2

Your approach is for the following question: there are 5 commodities A B C D F and we have to choose 2 . What is the probability of choosing B in the remaining 2?

thanks stolyar... but just one thing. Once E has been taken isnt our question reduced to 5 commodities from which we have to pick 2. So why cant we use the same logic as mine in that case.

1. My favorite football team to infinity and beyond, the Dallas Cowboys, currently have the best record in the NFL and I’m literally riding on cloud 9 because...

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...