Evaluate C(8,4)?/????????

Evaluate C(8,4)

The answer is [3] 70, so C(8,4) = 70

http://www.wolframalpha.com/input/?i=8C4&a=*MC.8C4…

Good luck!

Source(s): Experience

C(8,4)=
8C4=
70

C(8,4)=8! / 4!(8-4)! = 70

C(8,4)

FAST WAY

Start with 8 and count down so get a TOTAL of 4 numbers
*******************************************************************
Start with 1 and count up to 4

8*7*6*5
*********
1*2*3*4…………Cancel the 2*3 with the 6 and cancel the 4 with the 8 leaving a 2 up top

2*7*5

70…………ANSWER

Another Example
C(6,2)

6*5
****
1*2

30/2= 15

TOUGH/EASY one

C(20,18)……could be a LONGgggggggggg problem
UNLESS you change it to
C(20,20-18)=C(20,2)

20*19
*******
1*2

10*19=190
CAN ONLY DO THIS WITH COMBINATIONS, NOT WITH PERMUTATIONS

P(10,3) shortcut

10*9*8……=…..720

P(12,3)………….12*11*10=………….1320

P(20,18)..GET A CALCULATOR

C(n,k) = n! / (k! (n-k)!)

= 8! / (4!(8-4)!)
= 40320 / (24(24))
= 40320 / 576
= 70

Answer 6

see your previous problem!

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