41 tuning forks are so arranged that every fork gives 5beats with the next. The last fork has a frequency that is double of the first. The frequency of first fork is

Given      Number of forks=41     Number of beats=541 Tuning forks arranged in series in increasing order of frequency.Each fork gives ‘5’ beats with the preceeding one means, frequency of each fork is ‘5’ more than the preceeding one   Hence 41 frequencies are in arithmetic progression with common difference is -5hz It is given that the frequency of last one f41  is double of first one f1  We know formula fn=f1+(n−1)d .         fn=f41    fn=2f1   n=41 ,d=5                  f41=2f1           2f1=f1+(41−1)5             f1=40×5        ∴f1=200Hz