Expert: Paul Klarreich - 5/28/2008

Question
QUESTION: how would i figure out the number of minutes that have passed between say 19:00:34 and 20:07:02

John

ANSWER: Questioner:   John
Category:  Advanced Math
Private:  No
 
Subject:  figure out minutes within time
Question:  how would i figure out the number of minutes that have passed between say 19:00:34 and 20:07:02

John
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Hi, John,

All you do is subtract, but you might have to do some (borrowing, exchanging, converting) of minutes and seconds.
Later time: 20 h  07 min   02 sec
minus       19 h  00 min   34 sec

-- becomes ---

Later time: 20 h  06 min   62 sec  << exchanged
minus       19 h  00 min   34 sec
--------------------------------------
gives:       1 h   6 min   28 sec

You want minutes?  1 h = 60 min.  Make it 66 min  28 sec.


---------- FOLLOW-UP ----------

QUESTION: Paul,
THANKS for the quick reply. One more question, sorry, why do you have to have the exchanged part? and how did you come up with it (the new exchanged time)?

John

Answer
QUESTION: Paul,
THANKS for the quick reply. One more question, sorry, why do you have to have the exchanged part? and how did you come up with it (the new exchanged time)?

John

............................
You don't have to -- that's just how subtraction works.  You probably do it automatically.  

How do you subtract 34 from 2?  You need some number bigger than 34 to make it work.  So you take one of the 7 minutes, convert it to 60 seconds, then combine it with the 2 seconds.  

You have been doing this since the third grade; you just don't give it any thought nowadays, because it's automatic.