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SAI International School
Sub – Mathematics
Class - IV
Topic – TIME
Sub topic – Addition and Subtraction of time
Addition and subtraction of time is different from addition of ordinary numbers.
This is because conversion from one unit to another is not done in tens. Lets
study the following examples to understand.
ADDITION OF TIME:
Example 1: Gopal took the metro to go to his office. The metro took 24
minutes 40 seconds. Then he had to walk for 15 minutes 30 seconds. How
long did he take to reach office?
Answer: Time taken by Gopal to go to his work = 24 minutes 40 seconds
+ 15 minutes 30 seconds
We know, 60 seconds = 1 minute.
Min Sec
1
24 40
+ 15 30
40 10
Step 1: Add the seconds.
40 sec + 30 sec = 70 sec; 70 sec = 1 min 10 sec [1 minute = 60 sec]
Write 10 sec in the sec column and carry 1 min.
Step 2: Add minutes and the carried over minute.
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