Not sure if you want seconds in 3 and 1/2 hours or in three 1/2 hours.
If it is the first case then
1 hour is 3600 seconds, hence 3 hours is 10800 seconds. Add to this the number of seconds in half hour which is 1800 to get a total of 12600 seconds
If it is the second case then
1/2 hour is 1800 seconds, hence 3 half hours is 5400 seconds.
12,600 seconds.
There are 19800 seconds in 5 and a half hours.
2 and a half hours is 90 seconds.
10.5 hours is 37,800 seconds.
Half an hour is 1800 seconds. 3 half hours are 5,400 seconds.
91/2 hours is 34,200 seconds.
10,800 seconds.
108,030 seconds.
210 seconds
Three hours.
There are: 90*60 = 5,400 seconds
There are 86,400 seconds in a day (24 hours x 60 minutes x 60 seconds). Therefore, in a day and a half (36 hours), there would be 129,600 seconds (36 hours x 60 minutes x 60 seconds).