Question

Mr a's tv has only 4 channels.All of them quite boaring so he naturally desires to switch the channel after every 1 minute. The probability that he is back to his original channel for the first time after 4 minutes is

Answer 1

if A,B,C,and D are chennel , and he can change the channel in both side( assume cyclic arrenge ment , becaus he can either increase the channel no or decrease the channel no ) so for after 4th time he will get the original (1st ) channel there is only one way . and now we can see he has two ways to go so total number of ways he can change channel is 2*2*2*2=16

P(required) 1/16.