The answer depends on the units used for 39.51 It should be blindingly obvious to anybody that the answer for 39.51 microseconds and 39.51 days, for example, will be very different.
It is: 9.5
40
36 seconds
If that's 4.72 seconds, it rounds to 5
40.00
4000
36 seconds
27.3
It is: 9.5
40
40
36 seconds
The answer is 9.8 seconds.
36 seconds
2.6 seconds.
42.59
If that's 4.72 seconds, it rounds to 5