Which final output ratio will give the highest output speed?

• A. 1.0:1
• B. 0.5:1
• C. 0.25:1
• D. .67:1

Answer: (D)

The key idea is how a final drive ratio controls speed. The final output speed is the engine speed scaled by the gear ratio in the drive system. A larger ratio means more of the engine’s speed is passed to the output, so the output turns faster. When you compare ratios, the one that gives the greatest speed is the largest number you’re multiplying by (up to the point where the system can still deliver the required torque and control).

Looking at these options, the values below or equal to 1 show how much output speed you get relative to the input. The largest value in that set is 1.0:1, which would yield the highest speed in a straightforward interpretation. If your material uses a convention where the ratio is expressed as an overdrive-like figure (less than 1) but still treated as the relative speed the output can achieve within that context, then the largest such value below 1—0.67:1—would be the greatest speed among the choices given.