nasa uses a launch clock to measure time befo...
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?\n-3 hours 15 minutes, because all the preparation times add to 3 hours and 15 minutes\n-3 hours 35 minutes, because all the preparation times add to 3 hours and 35 minutes\n-2 hours 35 minutes, because all the preparation times add to 2 hours and 35 minutes\n-2 hours 15 minutes, because all the preparation times add to 2 hours and 15 minutes
Answer
# Explanation:
## Step1: Add up preparation times
Add 2 hours 15 minutes (preparations on - base), 20 minutes (travel to launch - pad), and 40 minutes (pre - launch checks).
2 hours 15 minutes+20 minutes + 40 minutes = 2 hours 75 minutes.
Since 60 minutes = 1 hour, 75 minutes = 1 hour 15 minutes. So 2 hours 75 minutes = 3 hours 15 minutes.
The launch clock measures time before and after lift - off. The time before lift - off is represented as negative time. So the astronauts should begin preparation 3 hours 15 minutes before lift - off, which is - 3 hours 15 minutes.
# Answer:
- 3 hours 15 minutes, because all the preparation times add to 3 hours and 15 minutes