elapsed time

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Archive : 2006 : April : 19

elapsed time
By BetsyC

Hi! I learned a strategy for teaching elapsed time at a workshop about three years ago that is awesome. Now that I teach this difficult skill using the techniques this teacher shared my third graders have ALWAYS been able
to find elpased time. I'm going to do my best to explain it, but it's really one of those things you need to see. If you can't make any sense out of my words, maybe I could scan an example and send it to you via e-mail. Here goes:

1. Jamie put a pizza in the oven at 1:25. It cooked for 30 minutes. What time was it when the pizza was ready to eat?

The student draws

a t-chart. At the top on the left side write the start time-1:25. On the top at the other side write min. Now, in between the two draw an arrow pointing up to show that we are counting up. Next, make several horizontal lines going down the t-chart. Under "min." write 5, 10, 15, 20, 25, 30. On the other side, under 1:25, count up the time until it is on the same line as "30." The left side should say 1:30, 1:35, 1:40, 1:45, 1:50, 1:55. The answer is 1:55 and I have the kids circle it.

This will work with virtually any kind of elapsed time problem.

2. Kyle's soccer practice started at 4:10 and lasted until 4:40. How long did soccer practice last?

The student draws a t-chart. At the top on the left side write the start time-4:10. On the top at the other side write min. Now, in between the two draw an arrow pointing up to show that we are counting up. Next, make several horizontal lines going down the t-chart. Under the start time count up at five minute intervals until it shows 4:40. Under min. count up by fives until you are on the same line as 4:40 and there you have how much time has passed! (30 min.)

3. Tamia went to the mall at 2:20 and shopped for one hour and 10 minutes. What time was it when Tamia left the mall?

This time you will complete two t-charts, one for the hours and the other for minutes. Do the hour chart first. The student draws a t-chart. On top of the left side write 2:20. On the top of the right side write hours. Don't forget the arrow pointing up! Now make several horizontal lines and label the first underneath hours with 1. Now move 2:20 to 3:20. The next thing to do is create the minutes t-chart and use 3:20 as the start time.

I promise that if you can figure out what I'm trying to explain this will work for your students. My students always love it! One thing they have to learn to look for is whether the problem requires them to find the minutes elapsed or to find a new time. That's how they know which side of the t-chart to work first. They will eventually get to the point where they don't even need the t-charts. If your time has minutes that aren't at intervals of five you can still do it. For example, if the time is 2:12 just add five to that to get 2:17. If you are subtracting time the arrow should point down. You have to teach this step-by-step but they will quickly catch on.

Please let me know if you have anyquestions. Thanks!
Betsy