Question

If the frequency of a sound wave produced by an oscillating piston of a long tube filled with air is 20 Hz, then how many oscillations does the piston complete per minute?

Answer 1

Frequency is $$20\ \text{Hz}$$, i.e. 20 oscillations per second. In one minute: $$20\ \text{Hz}\times 60\ \text{s}=1200$$ oscillations. So the piston completes 1200 oscillations per minute.