Work out number of minutes from 13:55 to next hour (14:00) which is 5 minutesCalculate number of whole hours until 15:20 so 1 whole hour = 60 minutesCalculate number of minutes from 15:00 to 15:20 so 20 minutesAdd 20 + 60 + 5 minutes = 85 minutes = 1 hour 25 minutes