Subtracting Time
To take away time, we subtract the minutes from the minutes and the hours from the hours. Line them up in two columns to keep them tidy.
Key idea
If there are not enough minutes to subtract, borrow 1 hour and change it into 60 minutes. Remember: 1 hour = 60 minutes.
Borrowing an Hour
When the top minutes are smaller than the bottom minutes, take 1 hour from the hours and add 60 minutes to the top.
Worked example
4 hours 15 min − 1 hour 30 min. We cannot do 15 − 30, so borrow: 4 hours becomes 3 hours, and 15 min becomes 75 min. Now 75 − 30 = 45 min and 3 − 1 = 2 hours. Answer: 2 hours 45 minutes.
Remember
- Subtract minutes from minutes, hours from hours.
- 1 hour = 60 minutes.
- Borrow an hour when the minutes are too small.