Answer:
548.5 Hz
Step-by-step explanation:
We are given that
Frequency of source=500 Hz
Speed of train=30m/s
Speed of sound in air=339m/s
We have to find the frequency of the bell to an observer riding the train.
The apparent frequency for the listener

Where
Frequency of source
=Speed of sound
=Speed of source
Using the formula
The apparent frequency of the bell to an observer riding the train=

Hence, the apparent frequency of the bell to an observer riding the train=548.5 Hz