- Subjects:Real-World Math, Time, Teacher Tips and Strategies

# Teaching Elapsed Time: Strategies That Work

- Grades: 1–2, 3–5, 6–8

Elapsed time, and all time concepts, are tricky to teach. Students seem to either “get it” or not, and there doesn’t seem to be a correlation between proficiency at other mathematical skills and the ability to calculate time. Why? For one, time is more abstract. There isn’t an algorithm to turn to in a pinch. Even adding and subtracting time presents problems when going over an hour span. Another reason might be that students have limited clock experiences. I know that my students rarely have clocks in the home and not many people wear watches anymore with the advent of cell phone clocks. Finally, teachers might be to blame. How often do you tell your students, “Three minutes” only to have five or ten go by before you realize it? No matter the reason, elapsed time can be especially difficult to master. Here are some tips and favorite strategies for teaching elapsed time.

**Make Time Matter**

Hold students accountable for their time. If you say that they have five minutes to finish a task, set a timer and stick to it. Students have to own a sense of time for elapsed time to make any sense. Adults, both parents and teachers, tell kids, “Just a minute,” all the time. How often do we actually mean 60 seconds? Parents wake them up; teachers and bells tell them when class starts and ends. We say, “Lunch is in about a half-hour,” when what we mean is 22 minutes. Start engraining time in your day, every day, and students will start to internalize it themselves.

**Fix It Fast**

- If you have a whiteboard, use a timer when you give limits and stick to it.
- When you speak in class, be exact in what you mean.
- Use a variety of ways to say time, such as, "a quarter till" instead of "15 minutes to."

**Real Life Rules**

One of the eight mathematical practice standards in Common Core encourages the use of real-life situations. It turns out that real life and elapsed time go well together. This is a good thing, say Kamii and Russell in their *Journal for Research in Mathematics* article entitled “Elapsed Time: Why Is It So Difficult to Teach?” Their research suggests, “Students must be encouraged to think about durations in daily living and do their own thinking . . . ” in order to be successful at elapsed time.

**Fix It Fast**

- Make your sample problems relatable to your students. Use times and situations that matter to them, such as how long it is until lunch or when Mom needs to pick them up at the movies.
- Ask a time question every day. They work seamlessly into your transitions. Ask students how long they have until the end of the day or to figure out what time they started working. Simple and quick, but effective.
- Use book characters and events to create questions. Books with time in the plot, such as
*Time Remote*, are especially fun! - Incorporate the reading of functional texts and science projects. Cross-curricular ties strengthen memory.

**Stop Subtraction**

Don’t give your students the subtraction strategy for time! DON’T! What will happen when they have to go over an hour? What about when they have to convert hours to minutes? The problem with subtraction and the “algorithm” for time is that students who don’t truly grasp time are lost. They can’t transfer their knowledge from one kind of time problem to the next. Only teach students strategies that can be applied to other problems. If the strategy doesn’t work repeatedly, don’t do it!

**Strategies That Work**

I know, I just said not to teach algorithms, but there are some strategies that work. Strategies work, not algorithms. Students still have to understand and apply their knowledge in order to work the problem, but these two methods make it easier for students to be successful.

Using a T-chart to find elapsed time is an easy strategy for students. They can lay out their starting time and ending time in an organized way. It gives them an entry point for a problem, but when students are given an ending time and asked to move backwards a specific amount of time, the computation gets tricky.

*This is, by far, my favorite strategy for teaching elapsed time. I don’t know the creator of this strategy, but I would love to shake their hand. Mountains are an hour, hills are five-minute increments, and rocks are one-minute increments. Using a time line, students make a visual representation of their thinking. Not only is it a fast way to find solutions, but this strategy also lets you see exactly where students go wrong when they are having problems. There is no guessing what they meant, and they have to fully understand time. Finally, this strategy works for the student who can tell time fluently, and also for remedial students who cannot count more than five minutes at a time.*

To practice this strategy, I give students one question from a page of problems. Pairs of students draw their work on a piece of chart paper and then we hang them around the room. Each chart gets a letter assigned to it. Students then get the full assignment and walk around matching their questions with the work displayed by writing the letter of the answer chart next to the problem. It gives them practice while showing the common errors and how mistakes affect the problems.

**Share Your Strategies**

What other strategies do you use for elapsed time? I’ve heard of teachers making giant “walkable” clocks on their floor and of variations on the time line. What has worked in your classroom?

## Comments (22)

I love, love, love the ideas here; especially Mountains, Hills and Rocks! I can't wait to see all the light bulbs go off in our 5th grade class tomorrow! Thank you for sharing.

Yay! Thanks so much. I hope it will help. I love doing these mountains, hills, and rocks!

Thanks for these visuals on how to teach elapsed time! They will be so helpful with my RTI math group!

what happen when you have start time and elapsed time and not end time like

start tome is ending time elapsed time

5:00 3 hours and 57mintes

So I use the same strategy. The great thing about pebbles, hills, mountains is that you can start at the beginning or end. I would draw a line and put 5:00 on the start. Then we would go a hill (1 hour) and write down 6:00, then two more times so you get to 8:00. Then you go chunks of time forward, whatever makes sense for the kid, until they get to 57 minutes added on. The last time would be 8:57 (the final time.)

I absolutely love the mountains, hills and rocks strategy! I taught it to my daughter tonight and will teach it to my third grade class tomorrow.

Thank you for this web page and all your insightful tips!! It was very difficult explaining this to my cousin, but she finally got the hook of it with the "T-Chart". Great help!

Great! I'm glad it could help! I liked the T-Chart, but my kids like the mountains :)

great idea.

show some example so we can teach our child easily its difficult for the first time teaching.

Elapsed time is sometimes difficult for kids to understand!

Thank you! I'm trying to teach my son elapsed time and the book we are using was recommending the subtraction strategy. I just couldn't understand the logic in teaching a rule that doesn't always work. Thank you for posting another method.

Backwards N- although I usually turn it into a regular N as some students have difficulty making a backwards N. http://theorganizedclassroomblog.com/index.php/ocb-store/view_document/72-elapsed-time-backwards-n-strategy

We use the mountains and hills to teach elapsed time but we also have students plug the times into an SEF chart (S-start, E-elapsed, F-finish). This helps them organize their work and know which part of the problem they are missing. When students write the the time below the mountains and hills, I have them turn their paper sideways so they have room to write.

I turn the sheet sideways too! The chart is a good idea so they can visualize it in another way as well. I like that.

I have been using the as you call it the "Mountain, hills and rocks" methods for many years. One of the teachers had been having trouble with her students understanding elasped time. They had been working with time lines in history. So I just suggested a method very similar to this. It works great and the students can understand it.

I know it has been around (I learned it from my math coach who got it from another teacher in the district) but I couldn't find an originator. I like it so much more than the other methods because they can go forward or backward in time with it. Some of my kids will only know "subtraction" from third grade, and that really gets confusing when we move to harder problems!

Un'idea straordinaria!!!

When my students do their homework, I tell them to put B.T. (beginning time) on the top of their papers, then write the time they begin their homework. When they finish, they write E.T. (ending time) and write the time they finished. I don't tell them to solve it at first; I just want them to develop the habit of writing it. This helps build background knowledge of passing time. By the time I'm ready to introduce a formal unit on elapsed time, students have a working definition of elapsed time meaning "how long it takes," or "how much time passed." Then we try various strategies for solving so they can choose the one that works best for them.

Great idea! I can see that being really helpful in the early stages. I think it would be good for me to know as well AND they would have to be telling time at home!

Thanks! It has worked really well for my kids and saved a lot of headaches!

Love this idea!