Answer:
11 am
Explanation:
Bus A and Bus B leave the bus depot at 9 am.
Bus A takes 30 minutes to complete its route once
Bus B takes 40 minutes to complete its route once.
We solve this finding the Lowest Common Multiple of the minutes each bus uses to complete it's route
30 = 3 × 10
40 = 4 × 10
= 3 × 4 × 10
= 120 minutes
120 minutes after 9 am is
60 minutes = 1 hour
60 minutes = 1 hour
= 2 hours.
9am + 2 hours
= 11 am.
Therefore, they be back at the bus depot together at 11 am