SOLUTION: It is known from the past experience that 80% of the students in a school do their home work. Find the probability that during a random check of 10 students a)all have done their

Question 1188688: It is known from the past experience that 80% of the students in a school do their home work. Find the probability that during a random check of 10 students a)all have done their home work b) at the most two students have not done their home work c)at least one student has done the home work.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
All have done it is 0.8^10 (independent)=0.1074
at most two have not done it.
0 have not done it is 0.1074
1 has not done it is 10*0.8^9*0.2^1=0.2684
2 have not done it is 10C2*0.8^8*0.2^2=0.3020
That sum and the answer is 0.6778
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At least 1 student has done it is 1- nobody has done it which is probability <0.0001 (1 x 10^(-7)) or 0.2^10
so the answer is 1.000.
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