Measuring Elapsed Time | Elementary

Measuring Elapsed Time - Cycle 3

| Mathematics

How to Subtract Seconds, Minutes, and Hours?

Use subtraction to measure the elapsed time (duration) of an event.

Example

How much time has elapsed from 4 hours 54 minutes 51 seconds to 6 hours 46 minutes 33 seconds?

I write the subtraction by lining up the hours, minutes, and seconds.
I start by subtracting the seconds. Since it is impossible to subtract 51 s from 33 s, I regroup 1 min (60 s). So, I add 60 s to the 33 s. 60 s + 33 s = 93 s I subtract. 93 s - 51 s = 42 s
Next, I subtract the minutes. Since it is impossible to subtract 54 min from 45 min, I regroup 1 h (60 min). So, I add 60 min to 45 min. 60 min + 45 min = 105 min I subtract the minutes. 105 min - 54 min = 51 min
Finally, I subtract the hours. 5 h - 4 h = 1 h

A duration of 1 h 51 min 42 s has elapsed from 4 h 54 min 51 s to 6 h 46 min 33 s.

Addition is used to measure the elapsed time (duration) of several events.

Example

What is the total duration of two events that have a duration of 2 hours 32 minutes 59 seconds, and of 5 hours 39 minutes 30 seconds?

I write the addition by lining up the hours, minutes, and seconds.
I start by adding the seconds. 59 s + 30 s = 89 s
Since there are more than 60 s, I subtract 60 s from 89 s and regroup 1 min. 89 s - 60 s = 29 s
Next, I add up the minutes. 33 min + 39 min = 72 min
Since there are more than 60 min, I subtract 60 min from 72 min and regroup 1 h. 72 min - 60 min = 12 min
Finally, I add up the hours. 3 h + 5 h = 8 h