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Question

NASA uses a launch clock to measure time before and after lift-off. It takes 2 hours and 15 minutes of preparations on base, 20 minutes to travel to the launch pad, and 40 minutes of pre-launch checks once in the spacecraft. When should the astronauts begin preparation?

–3 hours 15 minutes, because all the preparation times add to 3 hours and 15 minutes

–3 hours 35 minutes, because all the preparation times add to 3 hours and 35 minutes

–2 hours 35 minutes, because all the preparation times add to 2 hours and 35 minutes

–2 hours 15 minutes, because all the preparation times add to 2 hours and 15 minutes

Answer 1

Before, below, loss are examples of negatives, while after, above, gain or profit are examples of positives.

All all the things mentioned in the question must happen before the launch, so we add the times together: 2hr 15m plus 20m plus 40m=2hr 15m plus 1hr (40+20 minutes=1hr)=3hr 15m. These must take place BEFORE launch, so this time is negative: -3hr 15m, answer 1.