Solving time word problems
Time problems ask you to find a starting time, an ending time, or how long something lasts (the duration). Read the question slowly and follow 4 steps so you do not rush and make a mistake.
Some questions use the 12-hour system (with a.m. and p.m.) and some use the 24-hour system (like 15:45). Change both times to the same system before you work.
Key idea
1 Understand what is asked. 2 Plan: decide whether to add or subtract. 3 Solve carefully, hour with hour and minute with minute. 4 Check the answer makes sense. Remember 1 hour = 60 minutes, so when the minutes reach 60 you carry 1 hour.
Worked example
Worked example
A film starts at 2:15 p.m. and lasts 1 hour 40 minutes. When does it end?
Plan: add the duration to the start time.
2:15 + 1 hour = 3:15, then + 40 minutes = 3:55.
The film ends at 3:55 p.m. Check: 3:55 − 1:40 = 2:15. Correct.
Remember
- To find an ending time, add the duration.
- To find a starting time, subtract the duration.
- When minutes reach 60, carry 1 hour.