Arithmetic Grade Four

Lesson One hundred and fifty-two: Subtracting Time

Borrowing from the hours column may take some getting used to. So, here's another example: 


       4:04
      -2:55
      ------
As you can see, 4 minus 55 just isn't going to work. You must borrow from the hours column. When you do this, you need to remember that one hour is worth 60 minutes! So, your revised problem will look like: 

      3:64
     -2:55
     ------
Now it's just a simple matter of 3 minus 2 and 64 minus 55, which yields an answer of 1:09.

Here's another example: 


  ORIGINAL PROBLEM:

       3:00          Obviously, we need to borrow from the 
     - 1:55          hours column to do this problem.
     -------

  PROBLEM AFTER BORROWING:

       2:60          Once we borrow one hour and regroup it
     - 1:55          into 60 seconds, the problem is very
    --------         easy to complete.
       1:05

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