90 x 0.75 = 67.5 minutes
67.5 minutes/60 = 1.125 hours
1 and 1/8
Natasha fell asleep for 1.125 hours.
We have been given that
Total time spent by Natasha on the beach = 1 1/2 = 3/2 hours
She fell asleep for 3/4 of time she was on the beach.
Hence, the time she fell asleep is given by
Therefore, Natasha fell asleep for 1.125 hours.