The light in a restroom operates with a 15-minute timer...

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Last Updated on May 11, 2023

Solution:

We are looking for two consecutive times (when the door opened) with a gap of more than 15 minutes, since only then the light would be off.

The light in a restroom operates with a 15-minute timer...

Since the door is opened at 8:31, the light shuts off at 8:46 and stays off until 8:54, so the light is off for 8 minutes.

Since the door is opened at 9:11, the light shuts off at 9:26 and stays off until 9:29, so the light is off for 3 minutes.

Finally, since the door is opened at 9:31, the light shuts off at 9:46 and stays off at least until 10:00, so the light is off for 14 minutes (at least until 10:00).

Thus, the light was off for a total of 8 + 3 + 14 = 25 minutes.

Answer: B

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Scott Woodbury-Stewart is the founder & CEO of Target Test Prep. A passionate teacher who is deeply invested in the success of his students, Scott began his career teaching physics, chemistry, math, and biology. Since then, he has spent more than a decade helping students gain entry into the world’s top business schools, logging 10,000+ hours of GMAT, EA, GRE and SAT instruction. Scott also served as lead content developer and curriculum architect for the revolutionary courses Target Test Prep GMAT, Target Test Prep EA, Target Test Prep GRE and Target Test Prep SAT Quant.