What is the engine's horsepower and rpm?

• A. 120 HP at 2000 rpm
• B. 150 HP at 2600 rpm
• C. 128 HP at 2300 rpm
• D. 100 HP at 1800 rpm

Answer: (C)

The key idea is reading the engine’s power output at a specific speed. Horsepower at a given rpm shows how much work the engine can do per unit time when turning that fast. If the spec sheet lists a pair like 128 HP at 2300 rpm, that means at 2300 revolutions per minute the engine is delivering 128 horsepower.

You can sanity-check this with the basic relationship between torque and horsepower: HP = (Torque in lb-ft × RPM) / 5252. Reversing that, the torque at 2300 rpm for 128 HP would be about (128 × 5252) / 2300 ≈ 292 lb-ft. So the 128 HP at 2300 rpm pairing not only matches the published rating but also corresponds to a plausible torque value at that speed.

Other options would imply different power at other speeds and, when cross-checked with the engine’s torque curve, typically wouldn’t align with the same engine’s expected performance at those speeds. Therefore, 128 HP at 2300 rpm is the correct pairing.