If the speed necessary for reaching port at a designated time is 21.6 knots and the pitch of the propeller is 22.5 feet, how many revolutions per minute will the shaft have to turn, assuming a 2% positive slip?

Correct Answer: Option A — 99 RPM

Calculate required RPM using: (Knots × 6,076.1) / (Pitch × 60 × (1 - slip)). With 21.6 knots, 22.5' pitch, and 2% positive slip: (21.6 × 6,076.1) / (22.5 × 60 × 0.98) = 131,243.76 / 1,323 = 99.2 RPM. Rounding to the nearest whole number yields 99 RPM.