Answer:
He need to start his homework from 7:10 sharp if he want to be in bed at 10:00.
Explanation:
Given Details are,
Time Required for social studies homework = 45 minutes
Time Required for science homework = 40 minutes
Time Required for math homework = 1 hour 15 minutes = 75 minutes
Time Required to get ready for bed = 10 minutes
Time when she will be on bed = 10 : 00
To find: Time when he start his home work.
Sum of all the given time ( in minutes ) = 45 + 40 + 75 + 10 = 170 minutes
170 minutes = 2 hours 50 minutes
2 hours before of 10:00 = 8:00
50 minutes before of 8:00 = 7:10
Therefore, He need to start his homework from 7:10 sharp if he want to be in bed at 10:00.