Doubt in Chapter 8 (The Number Properties Guide Prep )

[subhadeep2011]

Hi ,

I was going through the Basic of Data Sufficiency Chapter ( Chap 8 ) in "The Number Properties Guide" , and had a doubt regarding one of the rules mentioend there.

In the part "The Statements Never Contradict each other" ( Page 96) , the example states that the value of 'n' should be equal in each of the 2 statements.

However , I thought that each statement for DS should be taken individually ( they do not have any dependencies ) unless we are looking for option (C) - where both statements combined are sufficient.

Can somebody please explain this rule to me ?

[RonPurewal]

yes, you should take the two statements individually at first -- but that has nothing to do with the statement given here, which is a statement about the restrictions on DS problems overall.

the most accurate way to summarize this truth is the following:
on any DS problem, the two statements MUST HAVE AT LEAST ONE SOLUTION IN COMMON.
i.e., statement (1) and statement (2) are not allowed to be mutually exclusive.

note that you can use this fact to your advantage even if you don't get to the point of putting the statements together. here's how:
if you get mutually exclusive results from the two numbered statements, then your work for at least one of those statements is wrong.

this DOESN'T mean that you should be combining the statements at the outset of the problem -- but it does give you a helpful criterion in judging whether you've done the correct work.

[subhadeep2011]

Thanks for the clarification. Makes much more sense now.

[jnelson0612]

Great, thanks.