SOLUTION: round off 1hour 40minutes 42seconds to the nearest 0.25hour(show workings)

0.25 of an hour is 15 minutes.


    1 hour 40 minutes 42 seconds is between 1 hour 45 minutes and 1 hour 30 minutes and


    1 hour 40 minutes 42 seconds is closer to 1 hour 45 minutes than to 1 hour 30 minutes.



THEREFORE, 1 hour 40 minutes 42 seconds rounded to the nearest 0.25 hour is 1 hour 45 minutes, or  1   of an hour.    ANSWER