In the third question , we have not been informed whether the treasurer and the president need to be different people? Cant they both be same? In that case we may have 15*15 ways.
Is there something which I am missing? Pls help.
Common sense: you would not usually vest so much power in a single person (not if they are elected posts…in a dictatorship it would be different of course) so we would assume the default to be “different people” 🙂
In PnC questions, the wording often admits of more than one interpretation. In such cases I recommend “bhavnaon ko samjho” i.e. try to understand what is the most likely intent of the question-setter. It works more often than you might expect…
But all marbles of one colour are alike. So we need not arrange them AMONG THEMSELVES. It is like when we choose 3 people out of 10, the three don’t become identical (nor do the 7 rejected).
No, since 10P6 would be 10C6 *6! and not 8!. That would mean you have already fixed the position of the first two and are only arranging the new 6 people. Think about it! 🙂
CAT-holics 
hello..!!
in the last ques…why cant we say person 1 can slap rest 7….
person 2…rest 7… & so on..
thus total slaps = 7^8
You are multiplying instead of adding. If you add you will get the same answer 7 + 7 + 7 +…+ 7 = 56.
regards
J
In the third question , we have not been informed whether the treasurer and the president need to be different people? Cant they both be same? In that case we may have 15*15 ways.
Is there something which I am missing? Pls help.
Common sense: you would not usually vest so much power in a single person (not if they are elected posts…in a dictatorship it would be different of course) so we would assume the default to be “different people” 🙂
In PnC questions, the wording often admits of more than one interpretation. In such cases I recommend “bhavnaon ko samjho” i.e. try to understand what is the most likely intent of the question-setter. It works more often than you might expect…
regards
J
got it, thanks.This blog is excellent.
Hello J,
I am not able to understand the 1st question. Marbles are of different colors. Than it should be permutations.
Please clarify
But all marbles of one colour are alike. So we need not arrange them AMONG THEMSELVES. It is like when we choose 3 people out of 10, the three don’t become identical (nor do the 7 rejected).
regards
J
Hello J ,
Wouldn’t it be the same in case of the rowing question ? 10p6 or 10c6*8! ? Please help.
No, since 10P6 would be 10C6 *6! and not 8!. That would mean you have already fixed the position of the first two and are only arranging the new 6 people. Think about it! 🙂
regards
J