Solution
[tex]n=240[/tex]The probability of getting exactly 1 tail from three coins is
[tex]\begin{gathered} THH,HTH,HHT \\ \\ p=\frac{3}{2^3} \\ \\ p=\frac{3}{8} \end{gathered}[/tex]The expected value will be
[tex]\begin{gathered} E(X)=240\times\frac{3}{8} \\ \\ E(X)=90 \end{gathered}[/tex]The answer is 90 students
