E-Storepermutation and combination....impppppppp
27 Jul 2007 22:23:29 IST
permutation and combination....impppppppp
hii
well some basic formulas and points in permutation.....
1) 0! is always taken as 1
2)nCr = n! / (n-r)! (r)!
3)nPr = n! / (n-r)!
4)nCr + nCr-1 = n+1Cr
5)nC0 = 1 = nCn
6)n-1Pr + rn-1 + Pr-1 = n Pr
7
nCo + nC1 + nC2 + ............. + nCn = 2n
8) The no. of ways permoting n distant objects along a circle is (n-1)!
9)The no. of ways arranging n distant objects along a circle wen clockwise and anticlockwise arrangements are considered alike is = 1/2 (n-1)!
10)The no. of ways of arranging n persons along a round table so that no person have same 2 neighbours = 1/2(n-1)!
11)The no. of neckless that can b formed with n beads of diff. colour is = 1/2(n-1)!
12)The no. of diagonals of an n sided convex polygon is nc2 - n = n(n-3) / 2
n must be greater than = to 3
self written , some of my frnz need it
hope it helps :) :)
Comments (9)
samvedna kaloty
Cool goIITian
Joined: 11 Jul 2007 06:51:43 IST
Posts: 86
28 Jul 2007 06:56:58 IST
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hey it really workssss .. thanksss a lotttttt
30 Jul 2007 11:34:54 IST
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gud work.....
here are some more :
1) number of straight lines formed by joining n points , p of which are collinear = nC2 - pC2 + 1
2) number of triangles formed by joining n points , p of which are in same straight line = nC3 - pC3
3) In a plane , there are 2 sets of paraalel lines , one of m lines and other of n lines . If the lines of one set cut the lines of the other set , number of parallelograms formed = [nm(m-1) ( n-1) ] / 4
here are some more :
1) number of straight lines formed by joining n points , p of which are collinear = nC2 - pC2 + 1
2) number of triangles formed by joining n points , p of which are in same straight line = nC3 - pC3
3) In a plane , there are 2 sets of paraalel lines , one of m lines and other of n lines . If the lines of one set cut the lines of the other set , number of parallelograms formed = [nm(m-1) ( n-1) ] / 4
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