An engine develops 108 horsepower at 87 percent power. What horsepower would be developed at 65 percent power?

An engine develops 108 horsepower at 87 percent power. What horsepower would be developed at 65 percent power?

• A. 81 hp
• B. 72 hp
• C. 93 hp
• D. 60 hp

Answer: (A)

Power output scales with the percent of power used, so you can find the horsepower at a different percent by multiplying the known horsepower by the ratio of the new percent to the old percent. Compute 108 × (65/87) ≈ 80.7, which rounds to about 81 horsepower. The other numbers don’t fit this proportional change: 93 hp would imply about 86% power, 72 hp about 66% power, and 60 hp about 55% power. So the best match is 81 hp.

Power output scales with the percent of power used, so you can find the horsepower at a different percent by multiplying the known horsepower by the ratio of the new percent to the old percent. Compute 108 × (65/87) ≈ 80.7, which rounds to about 81 horsepower. The other numbers don’t fit this proportional change: 93 hp would imply about 86% power, 72 hp about 66% power, and 60 hp about 55% power. So the best match is 81 hp.