60 seconds = 1 minute so 8400 seconds = 8400/60 = 140 minutes. Simple!
3600 sec per hour, 60 sec per minute. 3600 x 2 + 60 x 20 = 8400
6 minutes, 11 seconds
3 minutes and 32 seconds
There are 5 minutes and 50 seconds
7 minutes, 28 seconds
9 minutes 18 seconds.
It is 3 minutes and 37 seconds
It is 11 minutes and 10 seconds
It is 2 minutes and 15 seconds
9 minutes and 23 seconds.
3 minutes 2 seconds
Six minutes, seven seconds.