15
A half hour is 30 min so there is two half hours in an hour
There are 60 seconds in one minute.
One week = 1,209,600 half-seconds.
6720
5,400 seconds are in 1 hour 30 minutes.
90 seconds
One and a half.
3600 t
90
9,000 seconds.
There are: 90*60 = 5,400 seconds