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Time in Minutes

  1. Mar 17, 2010 #1
    Hey all,

    I have a quick question about converting a difference between 2 times into minutes.
    I am modelling a 24 hour clock. The time 900 represents the time 09:00 and 1500 represents the time 15:00. If I subtract the two I get a difference of 600. If I want to convert this to minutes I would write (600/100)*60. There's my answer, but I can't seem to get my head round what (600/100) is doing. Why do I need to divide it by 100?

    This question was brought to you by an idiot.
     
  2. jcsd
  3. Mar 17, 2010 #2
    Because you represent hours as "hours*100", so to get "hours" back you need to divide by 100.
     
  4. Mar 17, 2010 #3
    12 and 24 hour clocks use the format: HH:MM, where H is an hour digit and M is a minute digit. Don't subtract the two times like that.
    15:00 - 09:00 = 6:00
    Six hours.
    There's 60 minutes in an hour, so multiply this by 60 minutes per hour.

    [tex]6 hour*\frac{60 minute}{1 hour} = 360 minutes[/tex]

    You don't need to divide by 100.

    Let's say you were looking at the difference between 7:00 and 8:45. Since there's 60 minutes in an hour, you can look at it like this.

    You need 60 minutes to reach 8:00 from 7:00. Then you need an additional 45 minutes to reach 8:45.

    Look at the difference between 7:00 and 10:30 now.
    You need 3 hours (10-7) and 30 minutes (30-0) to reach the end time. To get this into minutes, just multiply the 3 hours by 60 minutes per hour = (180 minutes), and add to 30 minutes to obtain 210 minutes.

    Hope this helps. Remember, there are no stupid questions; only answers can be stupid.
     
  5. Mar 17, 2010 #4
    Thanks a lot for the answers. Makes sense now :smile:

    The reason I had to do it like that however is for computer programming. Unfortunately coding a program to understand HH:MM is more complicated than doing HHMM-HHMM, though the former is so much easier to do in our heads :tongue:
     
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