Lesson 19 — Activity 2: Subtracting Time

Getting Ready

It is important to know how much time is left in a certain situation. Perhaps you need to know how much time you have before a doctor's appointment later this afternoon or how much time you have left in a testing situation.

You will be able to subtract time after this activity.

You will practise subtracting time in this activity.

Think about This:

Have you thought of an activity related to time? You will use this in the assignment for Activity 3.

Perhaps your doctor's appointment is for 5:15 p.m. It is now 12:26 p.m. and you want to know how much time you have before the appointment.

You can solve this problem by following the steps below:

Step 1:  Start at the current time. Let's deal with the minutes first. You know there are 60 minutes in an hour. Subtract the minutes from 60. This will tell you how many minutes are left in the current hour.

60 – 26 = 34

There are 34 minutes left before it is 1:00 p.m.

Step 2: Next, subtract the hour that you have now brought the time up to in step 1, from the hours part of the time you are looking at. In this case, your appointment is at 5:15 p.m.

5 – 1 = 4

You know that there are 4 whole hours left before your appointment.     


Step 3: Now you have to deal with the minutes. Add the minutes you calculated in step 1 to any minutes in the time you are looking at. In step 1 you had 34 minutes and the appointment is 15 minutes after 5:00 p.m.

34 + 15 = 49

There are 49 minutes in total.

Step 4: Add the hours from step 2 and the minutes from step 3 to find out the total time left.

4 hours + 49 minutes = 4 hours and 49 minutes

You have 4:49 left until your appointment.

                 Now you know how much time you have until your appointment.
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Try This:

You are writing a test today. You have until 4:30 p.m. to complete it. It is now 2:37 p.m. How much time do you have left to complete the test? Follow the steps outlined above.

Step 1: 60 – 37 = 23. There are 23 minutes left before it is 3:00 p.m.

Step 2: 4 – 3 = 1. There is 1 whole hour left to write the test.

Step 3: 23 + 30 = 53. There are 53 minutes in total.

Step 4: 1 hour + 53 minutes = 1 hour and 53 minutes

You have 1:53 left to write your test.