Respuesta :

jsblumen

Answer:

800 pulses

Explanation:

We have to convert everything to compatible units.

20kHz = 20e3 Hz

40 ms = 40e-3 s

Hz = 1/s => 1/20e3 s

[tex]\frac{40\times10^-3 s}{\frac{1}{20\times10^3} } = 800[/tex] pulses