Adding and Subtracting Time

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

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.

(Note: the easiest way to add 60 to the negative minutes is to start with 60 and subtract the minutes)

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

Subtract the Hours: 4-1 = 3
Subtract the Minutes: 10-5 = 5
The minutes are fine, 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