Question 1188688
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
-
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.