SOLUTION: What is the probability that it will rain 2 of the next 10 days when the probability of rain is 90%? Show the formula and your calculations.

Question 236927: What is the probability that it will rain 2 of the next 10 days when the probability of rain is 90%? Show the formula and your calculations.
Found 2 solutions by stanbon, edjones:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
What is the probability that it will rain 2 of the next 10 days when the probability of rain is 90%? Show the formula and your calculations.
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It's binomial with n = 10, p = 0.9, x = 2
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P(x=2) = 10C2(0.9)^2(0.1)^8 = 0.0000003645
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Cheers,
Stan H.

Answer by edjones(8007) (Show Source): You can put this solution on YOUR website!
I am assuming that the probability of rain is 90% PER DAY and that the question is what is the probability that it will rain on any 2 days EXACTLY, not more or less.
Prob=.9=x, Prob no rain=.1=y
we need to take the x+y binomial to the 10th power
(x+y)^10 the 2nd from the last term is x^2y^8
nCr=10C2=45 the coefficient in front of x^2y^8
So here's the formula:
prob=
.
Ed
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