Round off 1hr 38mins 45secs to the nearest 1/4hr1.645833333 We need to round off the decimal 0.645833333 to the nearest 1/4 hr. 1/4 hour is 0.25 hours. Divide 0.645833333 by 0.25 to get 2.5833333 That rounds up to the whole number 3. So the answer is hours. Edwin