A patient was diagnose with some ailment. He was given five different tablets to take at night at an interval of 15 minutes.

How long will it take the patient to consume all the five tablets?

It will take him an hour to take all five tablets.

Suppose he takes the first tablet at 9:00 pm. He will take the second tablet at 9:15, the third at 9:30, the fourth at 9:45 and the last at 10:00.