Notes: As per the question, part of the tank filled in 1 hour by pipe A
and by pipe B
then, part of the tank filled by both pipes in 1 hour
So, Time taken by both pipes to fill part of the tank = 60 minutes
∴ Time taken to fill part
∴ We can say that tank will be filled at 11:45 AM.
Hence option [A] is correct answer.