Too many solutions!

Find the number of triples of positive integers ( x , y , z ) (x,y,z) satisfying x + y + z = 102 x+y+z=102 .

Notation : ( M N ) \dbinom MN denotes the binomial coefficient , ( M N ) = M ! N ! ( M N ) ! \dbinom MN = \dfrac{M!}{N!(M-N)!} .

( 101 3 ) \binom {101}{3} ( 101 2 ) \binom {101}{2} ( 102 2 ) \binom {102}{2} ( 103 2 ) \binom {103}{2}

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

1 solution

Md Zuhair
Oct 6, 2016

Here we can see that we have x + y + z = 102 x+ y +z = 102 for all + v e +ve integral solutions. We know that if we need to do partitions for n n distinct things into 3 3 divisions and they are non negetive integers then think about lets say there are 102 102 balls and we have to divide in 3 3 divisions . then we need 2 2 sticks for this division but they can be placed any where so between two sticks we may also get 0 0 balls. So we see for 102 102 balls is we place \(2 ) sticks of partitions then 103 C 2 103C2 are ways to arrange them will be our answer similarly for n n balls and r r partions our formulae will be n + r 1 C r 1 n+r-1Cr-1 , But ( x , y , z ) (x,y,z) is + v e +ve integral then x > 0 x>0 , y > 0 y>0 and z > 0 z>0 or x > = 1 x>=1 and y > = 1 y>=1 and z > = 1 z>=1 or now x 1 = x x-1=x' , y 1 = y y-1=y' and z 1 = z z-1 = z' . Hence Now putting x + y + z = 99 x' + y'+ z' = 99 . From the previous formulae x x' , y y' and z z' are brought for non negetive. Hence our number of triplets ( x , y , z ) (x,y,z) for only +ve integers will be 99 + 3 1 + C 3 1 99+3-1+C3-1 = 101 C 2 101C2 .

Nice solution but please do improve LaTeX! :D

Sahil Silare - 4 years, 8 months ago

Log in to reply

You did'nt upvoted.

Md Zuhair - 4 years, 8 months ago

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...