Elapsed Time Problems
Grade 4 students learn to calculate elapsed time in Saxon Math Intermediate 4 using a jumping strategy on a mental number line. Elapsed time is the amount of time that passes between a start and end time. Students break the problem into easy chunks: start at 2:40 PM, jump 20 minutes to 3:00 PM, jump 1 hour to 4:00 PM, then jump 10 minutes to 4:10 PM—totaling 1 hour and 30 minutes. This method avoids confusion from direct subtraction across the 60-minute boundary.
Key Concepts
New Concept Elapsed time is the difference between two points in time.
What’s next Next, you'll use this concept to solve problems by finding the time that passes between a start and an end time.
Common Questions
What is elapsed time?
Elapsed time is the amount of time that passes between a start time and an end time. For example, if a movie starts at 2:00 PM and ends at 3:30 PM, the elapsed time is 1 hour and 30 minutes.
What is the jumping strategy for finding elapsed time?
Start at the earlier time, then jump in easy chunks—first to the next hour, then in full hours, then in remaining minutes—until you reach the end time. Add up all your jumps to find the total elapsed time.
Why is direct subtraction tricky with time?
Unlike regular subtraction, time uses a base-60 system for minutes, not base-10. So 4:10 minus 2:40 cannot be solved by simply subtracting 240 from 410. The jumping method avoids this confusion by counting forward in natural chunks.
How many minutes are in an hour?
There are 60 minutes in one hour. This is why we jump to the next hour first—getting to a round hour makes the rest of the counting much easier and avoids errors.
How do you solve elapsed time word problems?
Identify the start time and end time. Use the jumping method: jump to the next hour, count full hours forward, then count remaining minutes. Add all the jumps together for the total elapsed time.
What are examples of elapsed time in real life?
Elapsed time is used to figure out how long a recipe takes to bake, how much time you spent at school, how long a car trip lasted, and when an event will end if you know the start time and duration.