SOLUTION: how many dice must be thrown so that the probability of obtaining at least one 6 is at least 0.99?

Question 970234: how many dice must be thrown so that the probability of obtaining at least one 6 is at least 0.99?
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
Look at it from the probability of NOT rolling a 6.
That is (5/6)^x power. it is (n-1)/n or (1-(1/n)^x-1 *(1/n)
For the dice example it is (5/6)^(x-1) * (1/6)<0.01
Can take log of both sides base 10
(x-1)* (log 5/6)-log 6 < -2 log (1/6)=log 1-log (6), and log (1)=0. log 0.01=-2
(x-1) * (-0.079)-0.778 < -2
-0.079 x +0.079 -0.778 <-2
-0.079 x < -1.301
divide both sides by (-0.079)
x=16.46
to be at least 0.99, we need 17 throws.

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