Questions about the world of GRE Math from other sources and general math related questions.
safirshahbaaz90
Students
 
Posts: 23
Joined: Wed Jul 09, 2014 4:02 am
 

Confusion in Probability Question

by safirshahbaaz90 Mon Aug 11, 2014 11:51 am

Hi Tommy,

In question 24 in the Probability section of the 5 lb book, we count (2,6) and (6,2) as separate entries but not (4,4). Why shouldn't (4,4) be considered twice?

Also, explanation for question 34 tells not to double count certain entries. But why are we doing so in question 24?

I understand that only 1 question has to be posted per topic but I feel that these 2 questions are interrelated and so am posting them in the same topic. I hope this is OK.

Regards,
Safir
tommywallach
Manhattan Prep Staff
 
Posts: 1917
Joined: Thu Mar 31, 2011 11:18 am
 

Re: Confusion in Probability Question

by tommywallach Wed Aug 13, 2014 10:21 pm

Hey Safir,

Think of it this way:

2,6 represents a two on the first roll and a six on the second
6,2 represents a six on the first roll and a two on the second
But 4,4 represents a four on the first roll and a four on the second...see the issue? It can't be reversed.

As for 34, there's no conflict. BOTH questions are telling you NOT to double count.

-t