Question 1064881
np=10 mean
np(1-p)=variance=5
sd=sqrt (5) or 2.236
probability of 13 or more is (13-10)/2.236=probability z >1.342, which is 0.0898

The probability is 20C13 (0.5^13)(0.5^7)=0.0739, which is the exact probability.