A woman has 10 keys and only one key will open the lock. She tries the keys at random. What is the probability that she will open the lock on her 5th try?
Q1. A woman has 10 keys and only one key will open the lock. She tries the keys at random. What is the probability that she will open the lock on her 5th try?
Answer: 1 / 10
Explanation: The probability of not opening the lock on the first 4 tries is (9/10) * (8/9) * (7/8) * (6/7) = 6/10 = 3/5. The probability of opening it on the 5th try is 1/6 (since 6 keys are left and only one is correct).