Permutations And Combinations

Question
CBSEENMA11014279

There are 5 doors in a room, 2 on one side and 3 on the other side. A man wishes to enter the room from the side with two doors and get out from the other side. In how many ways can this be done?

Solution

                                    
Number of ways in which he can enter = 2
rightwards double arrow                         m = 2
Number of ways in which he can leave the room = 3
rightwards double arrow                          n = 3
By fundamental principle of counting, the number of ways in which he can enter the room from one side and get out from the outer side = m x n = 2 x 3 = 6

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Some More Questions From Permutations and Combinations Chapter

Determine K, so that K + 2, 4K – 6 and 3K – 2 are three consecutive terms of an A.P.