What is the ratio of the number of power strokes in the two-stroke cycle divided by the number of power strokes in the four-stroke cycle at a given value of engine revolutions per minute?

1/2

Explanation:

Lets take N is the speed of engine in RPM.

As we know that in two stroke engine, crank rotates one times in two stroke of piston. Every rotation of crank gives one power stroke. It means that two stroke give one power stroke.

On the other hand in four stroke engine, crank rotates two times in 4 stroke of piston. It means that 4 stroke of piston gives one power stoke.

So we can say that the ratio of number of power stroke in two stroke engine to the number of power stroke in four stroke engine is 1/2.