Answer: 72×24÷(24+40) = 27.
****BUT THAT IS WRONG*** The actual correct answer is any number between zero and 72.
Explanation:
P(has beard) = #(with beard) / (#(with beard) + #(without beard))
Expected beards in N trials = N × P(has beard)
WHY THAT'S WRONG:
You do not get a random sample by choosing the first 64 men walking by. Write that on the board 100 times!!