Three persons enter in a lift at the ground floor. The lift will go up to 10th floor. The number of ways, in which the three persons can exit the lift at three different floors, if the lift does not stop at first, second and third floors, is equal to .
Answer
210
Solution
Floors at which a person can exit: 4th to 10th 7 floors
The three persons must exit at three different floors.
First person: 7 choices, second: 6 choices, third: 5 choices
Number of ways = 7 6 5 = 7P3 = 210
Answer: 210