Answer: 11am
Step-by-step explanation:
To solve this, we have to calculate the lowest common multiple of 20 and 30. This will be:
20 = 20, 40, 60, 80, 100
30 = 30, 60, 90, 120, 150.
Here, the lowest common multiple is 60.
Therefore, we add 60 minutes to 10am. This will be:
= 10am + 1 hour
= 11 am
The next time that both buses leave at the same time would be 11am