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Question: Answered & Verified by Expert
5 persons entered a lift cabin on the ground floor of a 7 floor house. Suppose that each of them independently and with equal probability can leave the cabin at any floor beginning with the first. The probability of all the 5 persons leaving the cabin at different floors, is
MathematicsProbabilityTS EAMCETTS EAMCET 2018 (04 May Shift 1)
Options:
  • A 3602401
  • B 554
  • C 518
  • D 5!7!
Solution:
1090 Upvotes Verified Answer
The correct answer is: 554

The number of floors of the building except ground floor is 6.

The number of ways that the five persons can leave 6 floors is 65.

 The total number of cases is 65.

The number of ways that the five persons can leave in different floors is 6P5.

Probability =6P565

=6!5!·165

=7201296

Probability =554.

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