Telling Time - Subrtacting Time

Telling Time - Clocks

How do you subtract time?

When subtracting time you do not look at each digit. You look at the minutes as a whole. In the problem below you can not subtract 52 minutes   from 15 minutes (15 - 52 = ???), because 15 is smaller. You must borrow.

5 hours 15 minutes
- 1 hour 52 minutes
???????????????
How do you do this? You go to your hours and take 1 away. (5 - 1 = 4hours) 
You now have 4 hours.
An hour equals 60 minutes. You add the 60 minutes to the 15 minutes. 
(60 + 15 = 75 minutes) This gives you 75 minutes. Your problem now looks like this.
4 hours 75 minutes
- 1 hour 52 minutes
Now you are able to subtract.
4 hours 75 minutes
- 1 hour 52 minutes
3 hours 23 minutes
The answer is 3 hours and 23 minutes.
Remember this:

You follow the same rules when you are trying to figure out what time it was so many hours and minutes ago?

Example:

sclock8.gif (2093 bytes) What time was it 3 hours and 45 minutes ago?

Turn this into a subtraction problem. The clock says it is 8:25. Subtract 3:45 from 8:25.

    8:25  --->regroup-->
- 3:45
  7:85
- 3:45

Now you are able to subtract. The answer is 4:40. 3 hours and 45 minutes before 8:25 was 4:40.

Example 2

sclock13.gif (2073 bytes) What time was it 3 hours and 50 minutes ago?

Turn this into a subtraction problem. The clock says it is 1:45. Subtract 3:50 from 1:45.

    1:45  --->regroup-->
- 3:50
  2:105
   - 3:50

 

It is easy to subtract the minutes 105 - 50 = 55. The hours can not be subtracted
2 - 3 = ??

You must look at the clock when you encounter a problem like this one. The hour hand is on the one. Take away 3 hours from this. When you back the clock up 3 hours from 1 you get 10. Add this to your minutes.

The answer is 10:55.

Links to Telling Time Lessons and Practice Pages 

How Do You Tell Time

Google Form Practice on Telling Time to 5-Minute Interval

Google Form Practice on Telling Time to 1-Minute Interval

Lesson on How to Add Time

Practice Adding Time

Lesson on How to Subtract Time