Adding and Subtracting Time

Add or Subtract the hours and minutes separately.
But you may need to do some adjusting if the minutes end up 60 or more, or less than zero!

Adding Times

Follow these steps:

  • Add the hours
  • Add the minutes
  • If the minutes are 60 or more, subtract 60 from the minutes and add 1 to hours

Like this:

Easy example: What is 2:45 + 1:10 ?

Add the Hours: 2+1 = 3
Add the Minutes: 45+10 = 55

The minutes are OK, so the answer is 3:55

Hard example: What is 2:45 + 1:20 ?

Add the Hours: 2+1 = 3
Add the Minutes: 45+20 = 65

The minutes are 60 or more, so subtract 60 from minutes (65-60 = 5 Minutes) and add 1 to Hours (3+1 = 4 Hours) ... so the answer is 4:05

 

Subtracting Times

Follow these steps:

  • Subtract the hours
  • Subtract the minutes
  • If the minutes are negative, add 60 to the minutes and subtract 1 from hours.

Like this:

Easy example: What is 4:10 - 1:05 ?

Subtract the Hours: 4-1 = 3
Subtract the Minutes: 10-5 = 5

The minutes are OK, so the answer is 3:05

Hard example: What is 4:10 - 1:35 ?

Subtract the Hours: 4-1 = 3
Subtract the Minutes: 10-35 = -25

The minutes are less than 0, so add 60 to Minutes (-25+60 = 60-25 = 35 Minutes) and subtract 1 from Hours (3-1 = 2 Hours) ... answer is 2:35

(Note: did you see how we changed "-25+60" to "60-25" ... that is perfectly fine and makes the calculation easier.)

 

 
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