Solving time word problems
Word problems tell a story about time. We use a simple 4-step plan to solve them clearly.
Key idea
1 Understand what is asked. 2 Plan which operation to use. 3 Solve step by step. 4 Check the answer makes sense.
Choosing add or subtract
To find an end time, add the duration. To find how long between two times, subtract.
Worked example
A bus leaves at 9:00 a.m. and the journey takes 2 hours 30 minutes. When does it arrive? Plan: add. 9:00 + 2 hours = 11:00, + 30 minutes = 11:30 a.m. Check: 11:30 − 9:00 = 2 h 30 min. Correct.
Worked example
Lina starts her homework at 8:00 p.m. and finishes at 9:20 p.m. How long did it take? This asks for a duration, so we subtract: 9:20 − 8:00 = 1 hour 20 minutes. Check: 8:00 + 1 hour 20 minutes = 9:20. Correct.
Remember
- End time: add the duration.
- Duration: subtract start from end.
- Always check your answer.