Question

Thirty beats are heard in one minute when two notes are played together. If the higher note has a frequency of 740 Hz, what is the frequency of the lower note?1) 742 Hz2) 738 Hz3) 739.5 Hz4) 740.5 Hz

Answer 1

ANSWER

$3)739.5Hz$

EXPLANATION

First, let us convert the frequency from beats per minute to beats per second (Hertz):

$\begin{gathered} 30\text{bpm}=\frac{30}{60}\text{beats per second} \\ \Rightarrow0.5\text{bps}=0.5Hz \end{gathered}$

To find the frequency of the lower note, we have to find the difference between the frequency of the higher note and the frequency calculated above.

That is:

$\begin{gathered} 740-0.5 \\ \Rightarrow739.5Hz \end{gathered}$

The answer is option 3.