Probability Question 331
Question: A man has bunch of 10 keys out of which only one can open the door. He chooses a key at random for opening the door. If at each trial the wrong key is discarded, then the probability that the door is opened on fifth trial is
Options:
A) $ \frac{1}{2} $
B) $ \frac{^{10}C_5}{10^{5}} $
C) $ \frac{1}{10} $
D) $ \frac{5!}{10!} $
Show Answer
Answer:
Correct Answer: C
Solution:
The probability that the door is opened in the fifth trial $ =\frac{9}{10}\times \frac{8}{9}\times \frac{7}{8}\times \frac{6}{7}\times \frac{1}{6}=\frac{1}{10} $
BETA
