Question

A six-sided die is rolled ten times. What is the probability that the die will show an even number at most eight times?

Answer 1

P(even)=1/2. P(odd)=1/2. Let x= number of even in ten rolls

P(x<=8) = 1-P(x>=9) = 1-[C(10,9)(1/2)^9 *(1/2)^1 + C(10,10)(1/2)*(1/2)^0]

=1-[C(10,9)(1/2)^10 +C(10,10)(1/2)^10]

=1-(1/2)^10[10+1

=1–11/1024

=1013/1024