The number of British thermal units that are changed into useful work is 1,700. The number supplied is 4,300 Btu. What is the thermal efficiency to the nearest whole percent?
A) 30%
B) 35%
C) 40%
D) 45%

Question

Quizplus · Accepted Answer

Thermal Efficiency = (useful work output / energy input) x 100%
Thermal Efficiency = (1,700/4,300) x 100%
Thermal Efficiency = 0.3953 x 100%
Thermal Efficiency = 39.53%
Rounding off to the nearest whole percent, the answer is 40%. Therefore, the best choice is C.

The Number of British Thermal Units That Are Changed into Useful