Subtracting Time ExpressionsDate: 10/09/2005 at 13:52:17 From: madison Subject: subtracting years,days,hours,minutes and seconds How do I subtract two amounts of time, like 5 years, 21 days, 4 hours, 32 minutes, 17 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds How would you subtract all the numbers together? Date: 10/09/2005 at 14:18:08 From: Doctor Ian Subject: Re: subtracting years,days,hours,minutes and seconds Hi Madison, Think about how we would do a subtraction like 214 - 86 ---- We could write this as 200 10 4 - 0 80 6 ------------- then we have to exchange items from larger groups for items in smaller groups. For example, we could exchange 1 group of 100 for 10 groups of 10: 100 110 4 - 0 80 6 -------------- And then we could exchange 1 group of 10 for 10 groups of 1: 100 100 14 - 0 80 6 -------------- And now we can just do the individual subtractions: 100 100 14 - 0 80 6 -------------- 100 20 8 = 128 Does that make sense? Dealing with time is the same idea, but the group sizes aren't 10's. There are 365 days in a year, so 5 years, 21 days, 4 hours, 32 minutes, 17 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds --------------------------------------------------- becomes 4 years, 386 days, 4 hours, 32 minutes, 17 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds ---------------------------------------------------- There are 24 hours in a day, so that becomes 4 years, 385 days, 28 hours, 32 minutes, 17 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds ----------------------------------------------------- There are 60 minutes in an hour, so that becomes 4 years, 385 days, 27 hours, 92 minutes, 17 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds ----------------------------------------------------- And there are 60 seconds in a minute, so that becomes 4 years, 385 days, 27 hours, 91 minutes, 77 seconds - 2 years, 93 days, 7 hours, 47 minutes, 24 seconds ----------------------------------------------------- And now you can just do the individual subtractions. Does this make sense? - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
Search the Dr. Math Library: |
[Privacy Policy] [Terms of Use]
Ask Dr. Math^{TM}
© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/dr.math/