COMEDK · Maths · 36. Probability
Five persons entered the lift cabin on the ground floor of an eight-floor apartment. Suppose that each of them independently and with equal probability, can leave the cabin at any floor beginning with the first floor, then the probability of all five persons leaving at different floors is
- A \(\dfrac{7}{{ }^7 P_5}\)
- B \(\dfrac{{ }^7 P_5}{7^5}\)
- C \(\dfrac{{ }^7 P_5}{5^7}\)
- D \(\dfrac{5!}{7^5}\)
Answer & Solution
Correct Answer
(B) \(\dfrac{{ }^7 P_5}{7^5}\)
Step-by-step Solution
Detailed explanation
There are 8 floors in the apartment, but the persons leave at any floor from the first to the eighth floor. Thus, there are 7 possible floors for each person to leave (1st, 2nd, 3rd, 4th, 5th, 6th, 7th, 8th floor). Each of the 5 persons can choose any of the 7 floors…
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