nCr = 320 and nPr = 86 what is n & r ?

Answer 1

This is not possible because NPr should be > nCr.

please check the question

Answer 2

If it's just one question, where n and r are the same for each equation, then there are no possible solutions.

If they are separate questions, then the easy way out is:
nCr = 320, for n = 320 and r = 1.
nPr = 86, for n = 86 and r = 1.

Answer 3

It depends on whether or not repetitions are allowed.
without repetition: nCr=n!/(r!(n-r)!)=320 in this case
nPr=n!/(n-r)!=86 in this case
with repetition: nPr= n^r=86 in this case
nCr=(n+r-1)!/(r!(n-1)!)=320 in this case

n!=1*2*3*4.....*(n-1)*n
r!=1*2*3*4......*(r-1)*r
(n-r)!=1*2*3*4........*(n-r-1)*(n-r)
etc
You can work it out from there, its just cancelling factors that are both on the top and bottom of the qoutients and substituting using simultaneous equations.

it is only possible with your values if you allow repetitions. just think about this logically from the given equations or try substituting n=3 and r=2 and you will see that nPr is less than nCr.
If repetition not allowed then you get nPr/r! which has to be greater than one with the given values and is therefore imposible.

il leave you to figure out the rest. ;)
good luck

Answer 4

nPr = n! / (n-r)! This would be used for a problem where order is important, such as: You have 20 people running a marathon, and 1st, 2nd, and 3rd place get a prize. Finding the possible combinations of winners (where order matters)-- think of it this way. You have 20 people who can get 1st place. Once 1st is won, there are 19 people who can get 2nd. After that, you have 18 people who can get 3rd. So the possible combinations of winners is 20*19*18, or 6840. Now, if order does NOT matter, you use nCr. Consider if there were only 3 prizes, but they weren't ordered by 1st, 2nd, 3rd. So you have 20 people, and you already know (from above) that you have 6840 possibilities to choose the 3 people. But since order doesn't matter, you divide by 3!, since 3! is the number of ways the 3 places can be ordered. Hope that helps!

Answer 5

n = total number from which to select
r = number being selected

Eg if selecting 5 from 9 then n = 9, r = 5

So:nCr = 320 and nPr = 86
Now nCr = nPr/r! so these figures are impossible!!

Answer 6

We know that nCr=nPr/r!
i.e.r!=nPr/nCr=86/320 which is a fraction
But r! is always a natural no.
Therefore,by given values it is impossible to find n&r

Answer 7

n is total no. of possibalities and I guess r is selected possibalities of happening of a particular event.

Answer 8

Neo = n
Retard = r