Adding and Subtracting Time

We will learn how to addition and subtraction of units of time.

1. Add 25 minutes 45 seconds and 15 minutes 25 seconds.

Solution:

Add Time

First add the seconds 45 + 25 = 70 seconds

Convert 70 seconds into minutes and seconds

70 seconds = 60 seconds + 10 seconds

Carry 1 minute to minutes column and write 10 in seconds column

Therefore, 25 minutes 45 seconds + 15 minutes 25 seconds = 41 minutes 10 seconds

3. Add 9 months 25 days 21 hours and 7 months 20 days 13 hours.

Addition of Months Days and Hours

Ans: 17 months 16 days and 10 hours

Step I: Add the hours

21 + 13 = 34 hours

             = 24 hours + 10 hours

             = 1 day 10 hours

Step II: Write 10 under hours and carry 1 to days.

Step III: Add the days.

1 + 25 + 20 = 46 days

                    = 30 days + 16 days

                    = 1 month 16 days

Step IV: Write 16 under days and carry 1 to months.

Step V: Add the months

1 + 9 +7 = 17 months

Write 17 under months


2. Add 5 weeks 4 days and 4 weeks 5 days

Solution:

Addition of Weeks and Days

First add days, 4 + 5 = 9 days

Convert 9 days into weeks and days

9 days = 7 days + 2 days

           = 1 week and 2 days

Carry 1 to week column and write 2 in days column.

Therefore, 5 weeks 4 days + 4 weeks 5 days = 10 weeks 2 days


3. Subtract 18 minutes 29 seconds from 24 minutes 15 seconds

Solution:

Subtraction of Time

First subtract seconds

Since we cannot subtract 29 from 15, we borrow 1 minute. So, 15 + 60 = 75 seconds

75 – 29 = 46 seconds

Write 46 in seconds column

Now subtract minutes 23 – 18 = 5 minutes, write 5 in minutes column

Therefore, 24 minutes 15 seconds - 18 minutes 29 seconds = 5 minutes 46 seconds


4. Subtract 7 years 6 months from 8 years 3 months

Solution:

Adding and Subtracting Time

First subtract the months


We borrow 1 year and subtract, 16 – 6 = 9 months


Write 9 in months column and now subtract 7 – 7 = 0


Write 0 in years column.

Therefore, 8 years 3 months - 7 years 6 months = 9 months


1. Subtract 6 hours 40 minutes from 8 hours 55 minutes


Step I: Subtract the minutes.

55 – 40 = 15 minutes


Step II: Subtract hours.

8 – 6 = 2 hours


Subtraction of Hours and Minutes

Ans: 2 hours 15 minutes


2. Subtract 10 hours 50 minutes from 12 hours 45 minutes.

Subtract Hours and Minutes

Ans: 1 hour 55 minutes

Step I: We cannot subtract 50 minutes from 45 minutes.

So borrow 1 hour from 12 hours.

1 hour = 60 minutes

60 + 45 = 105 minutes

Step II: Subtract minutes.

105 – 50 = 55 minutes

Write 55 under minutes.

Step III: 12 – 1 = 11 hours remain in hours

Step IV: Subtract hours.

11 – 10 = 1 hour

Step V: Write 1 under hours.


Questions and Answers on Adding and Subtracting Time:

I. Add the following.

1.

Hours

Minutes

  30

   20

+

  20

   05


                                           


2.

Hours

Minutes

  45

   48

+

  10

   12


                                           


                                                          

3.

Days

Hours

  33

   20

+

  45

   14

+

  50

   16


                                           


4.

Weeks

Days

  32

   4

+

  10

   6

+

  48

   5


                                           


                                                                 

5.

Hours

Minutes

Seconds

  17

   42

  30

+

  12

   36

  20

+

  15

   50

  50


            


   6.

Years

Months

  56

   10

       +

  43

   05

       +

  17

   11


                



II: Subtract the following.

1.

Hours

Minutes

Seconds

  16

   30

  20

-

  15

   20

  50


            


2.

Hours

Minutes

Seconds

  13

   23

  43

 -

  10

   22

  32


                







4th Grade Math Activities

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