Posted by **jelanietux** on Monday, June 20, 2011 at 6:18pm.

The members of a men’s club have a choice of wearing black or red vests to their club meetings. A study done over a period of many years determined that the percentage of black vests worn is 60%. If there are 10 men at a club meeting on a given night, what is the probability, to the nearest thousandth, that at least 8 of the vests worn will be black?

I know you're supposed to use combinations, but how do you write it all out?

- Algebra/Trig -
**Damon**, Monday, June 20, 2011 at 8:25pm
BINOMIAL DISTRIBUTION, yes uses Combinations

n = 10

probability of black = .6

probability not black = .4

prob 8 = C(10,8) .6^8 .4^2

= 45*.6^8*.4^2 = .121

prob 9 = C(10,9) .6^9 .4^1

= 10 *.6^9 * .4 = .040

prob 10 = C(10,10) .6^10 .4^0

= 1 *.6^10 * 1 = .006

sum = .121+.040+.006 = .167

I got the Combinations from Pascal's triangle but you can use a table or calculate

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

- Algebra/Trig -
**jelanietux**, Monday, June 20, 2011 at 11:22pm
thanks!

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