A searchlight on top of the watchtower makes 2 revolutions per minute. What is the probability that a man appearing near the tower will stay in the dark for at least 10 seconds? Choose the most appropriate option:
A) 5/6
B) 3/4
C) 2/3
D) 1/2
E) 3/5
The searchlight completes one revolution every 30 seconds.   The probability that the man's area will be lit up is 10/30=1/3.   The probability that he will stay in the dark is 1-1/3=2/3   The answer is 2/3.
<result>C</result>
A searchlight on top of the watchtower makes 2 revolutions per minute. What is the probability that a man appearing near the tower will stay in the dark for at least 10 seconds?