Forty one tuning forks are arranged in increasing order of frequencies such that every fork gives 5 beats with the next. The last fork has a frequency that is double the frequency of the first fork. The frequency of the first fork is

Options

A. 210
B. 400
C. 205
D. 200

Answer

D

Explanation

Number of beats formed by two forks is equal to the difference in their frequencies. Therefore, the frequencies of the forks form a arithmetic progression with common difference (d) is equal to 5 and number of terms is equal to 41. Let f be the frequency of the first fork.
Then `2f=f+(41-1)xx5impliesf=200Hz`.