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
40
40
It is: 9.5
27.3
36 seconds
36 seconds
2.6 seconds.
The answer is 9.8 seconds.
To round 28.872 to the nearest tenths of a second, we look at the hundredths place, which is 7. Since 7 is 5 or greater, we round up the tenths place from 8 to 9. Therefore, 28.872 rounded to the nearest tenths of a second is 28.9 seconds.
42.59