primes<60

[sujoy]

SIR the ques is:
if p &q be prime nos < 60 & x is a pair of distinct prime nos
then how many distinct sets of x are possible
please help
sujoy

 

[pka]

Your question is hard to interpret.
But there are 17 primes less than 60.
Combin(17,2) is the number of pairs with distinct members.
Is that what the question means?

 

[TchrWill]

Primes

If I understand you correctly, you are looking for how many pairs of primes are possible with the prime numbers below 60.

There being 17 primes lower than 60, and ignoring the order of the primes, there are 17C2 = 17!/[2!(15!)] = 272.

This considers the pair of 2,3 the same as the pair 3,2.

 

[sujoy]

dear sir
i am really not sure what the problem hints at
however the answer is 120=15*16/2
if you could find anything
thanks a lot
sujoy

 

[pka]

Sujoy wrote: “however the answer is 120=15*16/2”.
That happens to be combin(16,2)!
As two pointed out there are 17 primes less than 60, not 16.
So the answer, 120, is clearly wrong if the question is indeed about pairs.
Also, some wrongly discount the fact that 2 is a prime number.
That confusion may account for the given answer.

 

[sujoy]

thanking

SIR,
I WANT TO THANK YOU FOR CLARIFYINGT MY DOUBTS
THANK YOU VERY MUCH
WITH REGARDS
SUJOY

 

[Denis]

hey pka, this the 1st time you're called "Sir" ?

Sir Sujoy: for your information, it is considered impolite
to write everything in capital letters; means you are yelling.