Answer:
1070 Hz
Explanation:
First, I should point out there might be a typo in the question or the question has inconsistent values. If the tube is 40 cm long, standing waves cannot be produced at 42.5 cm and 58.5 cm lengths. I assume the length is more than the value in the question then. Under this assumption, we proceed as below:
The insert in the tube creates a closed pipe with one end open and the other closed. For a closed pipe, the difference between successive resonances is a half wavelength 
.
Hence, we have
.
The speed of a wave is the product of its wavelength and its frequency.
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Explanation:
Calculating this according to the m/s rate
Now solving the question
If the car goes 20 m/s mathematically we can generate it as
15 × 60 = 600 secs
If the car goes 20 meters per every second it means
The car will go 20 meters for 900 secs
Which is 900 ×20 = 18000m/s
=18000÷1000 = 1km
Therefore the answer is 18km
