On the 4 stroke cycle the cylinder fires every two turns of the crank.
For that cylinder to fire 200 times, it requires 400 turns of the crank.
That's for a single cylinder engine. If there are 4 cylinders evenly spaced, one of the 4 cylinders fires every half turn.
So for every full turn of a 4 stroke 4 cyl engine, two cylinders have fired; that is, two power pulses have occurred.
Therefore, if the crank turns 400 times in a minute, each cylinder will have fired 200 times, but if there are 4 of them, there will have been 4 x 200 = 800 power pulses in total in that minute period.
If you have a two blade prop, two blades pass by with each revolution, and there are 2 cylinder firings with each revolution. So when you spin the prop by hand, you come up on the compression stroke of one of the cylinders with each half turn of the prop, or each blade at the same clock position (props are usually installed to place the blade such that the top of a compression stroke is reached at roughly 10 o'clock blade position when standing in front facing it).
The result is the sound frequency on a 4 cyl two blade engine is same for both the propeller blade beat and engine exhaust pulse frequency (roughly 60-90 Hz from cruise to full power, and about 13 Hz at idle), which is the dominant frequency in the cockpit, and why ANR headsets, which work best at very low frequencies, are so much more effective than earplugs in airplanes.