 Addition and Subtraction of Time - Orchids The International School
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Addition and Subtraction of Time

The steps to add times are the following:

• Arrange the times in the column according to the hours, minutes, and seconds.
• Add the seconds. If the seconds are more than 60 then subtract 60 from it and add 1 to the minute.
• Add the minutes. If the minutes are more than 60 then subtract 60 from it and add 1 to the hour.
• Add the hours.

Example:

Add 5 h 20 minutes 54 seconds and 2 hours 12 minutes 12 seconds.

Solution:

Step 1: Arrange both the times column-wise.

Step 2: Add 54 seconds and 12 seconds. The sum is 66 seconds which is more than 60.

Step 3: Subtract 60 from the sum 66. Write the difference 6 in the second column and add 1 to the minute’s column.

Step 4: Add 20 minutes, 12 minutes, and 1 minute. Write the sum 33 in the minute’s column.

Step 5: Add 5 hours and 2 hours. Write the sum 7 hours in the hour’s column. • Sometimes hour may also end up to large.
• If the hour is more than 24 then subtract 24 from it and add 1 day.

Subtraction of time

The steps to subtract times are the following:

• Arrange the time in the column according to the hours, minutes, and seconds.
• Subtract the seconds. If the second’s value in the minuend is smaller than the value in the subtrahend then borrows 1 minute (60 seconds) from the minute’s column.
• Subtract the minutes. If the minute’s value in the minuend is smaller than the value in the subtrahend then borrows 1 hour (60 minutes) from the hour’s column.
• Subtract the hours.

Example:

Subtract 3 h 12 minutes 48 seconds from 5 hours 20 minutes 12 seconds.

Solution:

Step 1: Subtract 48 seconds from 12 seconds. Since 48 > 12. Borrow 1 minute (60 seconds) from the minute’s column.

Step 2: Now subtract 48 from (60 + 12) = 72 seconds. Write the difference in 24 seconds in the second column.

Step 3: Subtract 12 minutes from 19 minutes. Write the difference 7 minutes in the minute’s column.

Step 4: Subtract 3 hours from 5 hours. Write the difference of 2 hours in the hour’s column. Elapsed Time

Elapsed time is defined as the total time that has passed from the starting time to the ending time.

Steps to find the elapsed time:

• Note the start time.
• Note the end time.
• Subtract the start time from the end time.

Example:

Write the time elapsed for the given pair of clocks: Solution:

The time on the first clock is 1: 10

The time on the second clock is 8:20

Time elapsed is equal to the difference between 8 hours 20 minutes and 1 hour 10 min.  Did you know?  • -