Car sounding a siren while moving towards a wall: frequency of the echo heard by the driver

1. A.
   $\frac{V_1}{V-V_1}n$
2. B.
   $\frac{V_1-V}{V+V_1}n$
3. C.
   $\frac{V+V_1}{V-V_1}n$
4. D.
   $\frac{V-V_1}{V+V_1}n$

Tap an option to check your answer.

1. A.
   $\frac{V+V_{1}}{V-V_{1}}n$
2. B.
   $\frac{V-V_{1}}{V+V_{1}}n$
3. C.
   $\frac{V_{1}-V}{V_{1}+V}n$
4. D.
   $\frac{V_{1}}{V_{1}-V}n$

Tap an option to check your answer.