An engine on a test stand was operated at two fixed settings, each with an appropriate load. At the first setting, fuel consumption was 1 gal every 15 min. At the second setting, it was 1 gal every 20 min. The test took 10 h, and 37 gal of fuel were used. How long did the engine run at each setting?
A) The engine ran for 7 h at the first setting,
The engine ran for 3 h at the second setting.
B) The engine ran for 3 h at the first setting,
The engine ran for 7 h at the second setting.
C) The engine ran for 7.5 h at the first setting,
The engine ran for 2.5 h at the second setting.
D) The engine ran for 4 h at the first setting,
The engine ran for 6 h at the second setting.
E) The engine ran for 6 h at the first setting,
The engine ran for 4 h at the second setting.

Question

Quizplus · Accepted Answer

At the first setting, the engine used 1 gal every 15 min, so in 10 h (600 min), it used 600/15 = 40 gal. At the second setting, it used 37 - 40 = 3 gal. So, it ran for 3 gal * 20 min/gal = 60 min = 1 h at the second setting. Therefore, it ran for 10 h - 1 h = 9 h at the first setting.

An Engine on a Test Stand Was Operated at Two