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How Do You Subtract Time for Kids?

Published in Time Calculations 2 mins read

Subtracting time can be tricky, but it's like subtracting regular numbers with a little twist! Here's how you can do it:

1. Understanding Time Basics

  • Hours and Minutes: Remember that there are 60 minutes in one hour. This is important when "borrowing" or regrouping.

2. Setting Up the Problem

Write the two times you want to subtract, one above the other, aligning the hours and minutes:

  Hours | Minutes
 ------|--------
    5  |   30
  - 2  |   15
 ------|--------

3. Subtracting the Minutes

Subtract the minutes first:

  Hours | Minutes
 ------|--------
    5  |   30
  - 2  |   15
 ------|--------
        |   15   (30 - 15 = 15)

4. Subtracting the Hours

Now, subtract the hours:

  Hours | Minutes
 ------|--------
    5  |   30
  - 2  |   15
 ------|--------
    3  |   15   (5 - 2 = 3)

5. Dealing with "Borrowing" (Regrouping)

Sometimes, you might need to "borrow" from the hours if the minutes you're subtracting are larger than the minutes you're starting with. For example:

  Hours | Minutes
 ------|--------
    5  |   30
  - 2  |   45
 ------|--------

You can't subtract 45 from 30, so you need to borrow 1 hour (which is 60 minutes) from the hours column:

  • Cross out the 5 in the hours column and write a 4 (because you took one hour away).
  • Add 60 minutes to the 30 minutes, making it 90 minutes.

Now your problem looks like this:

  Hours | Minutes
 ------|--------
    4  |   90
  - 2  |   45
 ------|--------

Now subtract normally:

  Hours | Minutes
 ------|--------
    4  |   90
  - 2  |   45
 ------|--------
    2  |   45   (90 - 45 = 45,  4 - 2 = 2)

So, 5:30 - 2:45 = 2 hours and 45 minutes.

6. Example

Let's say a movie starts at 7:15 PM and ends at 9:30 PM. How long is the movie?

  Hours | Minutes
 ------|--------
    9  |   30
  - 7  |   15
 ------|--------
    2  |   15

The movie is 2 hours and 15 minutes long.

7. Key Takeaways

  • Always line up the hours and minutes.
  • Subtract the minutes first.
  • If you need to "borrow," remember that 1 hour = 60 minutes.

Subtracting time becomes easier with practice. Keep practicing and you will master it!

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