Answer:
Answer: 
 
835.29 Hz 
 
Explanation: 
 
When moving towards the source of sound, frequency will be given by 
 
f*=f(vd+v)/v 
 
Where f is the freqiency of the source, vd is the driving speed, v is the speed of sound in air, f* is the inkown frequency when moving forward. 
 
Substituting 800 Hz for f, 340 m/s for v and 15 m/s for vd then 
 
f*=800(15+340)/340=835.29411764704 Hz 
 
Rounded off, the frequency is approximately 835.29 Hz
ı hope ıts true
Explanation: