Adding and Subtracting Time Together
Some problems have both a plus and a minus. We work from left to right, one step at a time. Keep hours with hours and minutes with minutes.
Key idea
Do the first two amounts, then use that answer with the next amount. Regroup with 60 minutes = 1 hour when you need to.
Word Problems Step by Step
Read the story, decide what to add and what to take away, then work it out and check. Words like "in all", "altogether" and "then" often mean add. Words like "left", "how much longer" and "shorter" often mean subtract. Underlining the key words helps us choose the right step.
Worked example
1 hour + 30 min − 15 min. First: 1 hour + 30 min = 1 hour 30 min. Then take away 15 min: 30 − 15 = 15 min. Answer: 1 hour 15 minutes.
Remember
- Work left to right, one step at a time.
- 60 minutes = 1 hour.
- Check your answer makes sense.