Q: The frequency of B is 3% greater than that of A. The frequency of C is 2% less than that of A. If B and C produce 8 beats/s, then the frequency of A is

(a) 136 Hz

(b) 168 Hz

(c) 164 Hz

(d) 160 Hz

Ans: (d)

Sol: $\large f_B = f_A(1 + \frac{3}{100})$

$\large f_C = f_A(1 – \frac{2}{100})$

$\large f_B – f_C = 8 $

$\large f_A(1 + \frac{3}{100}) – f_A(1 – \frac{2}{100}) = 8$

$\large f_A = 160 Hz$