calculate the probability of randomly guessing at least 7 correct answers on a 10 questions true or false quiz to get a passing grade?

Question

anonymous · Answer

Remember the probability of k successes in a binomial trial
$$
g(k)=P[X=k]= \frac {n!}{k! \, (n-k)!} p^k (1-p)^{n-k}
$$
Here 
$$
p=q=1/2;
$$

anonymous · Answer

So in this case 
$$
g(k) =\frac 1 {2^{10}}  \frac {10!}{k! (10 -k)!}
$$
The answer should be
$$
g(7)+g(8)+g(9) + g(10)
$$

anonymous · Answer

$$

\frac{15}{128}+ \frac{45}{1024}+ \frac{5}{512}+ \frac{1}{1024} =\frac{11}{64}
$$