Elapsed TimeA new way to calculate elapsed time

Pennsylvania State Math Standard

PA Math Standard 2.3.3.C

Anchor M3.B.1.1

How do you figure out how much time has passed, or how much time will pass during a certain activity?

Do you… Picture a clock in your head, and count

through the hours and minutes with your fingers?

Actually look at a clock, and count through the hours and minutes?

Take a guess? Is there another way?????

The T-Chart Method To use the T-Chart method to figure out

elapsed time, first draw a T-Chart like the one below:

Let’s use the T-Chart to figure out this problem.

Brianna started her Algebra homework at 6:15. She finished at 6:50. How long did it take her to complete her homework?

First, identify your starting time by circling or highlighting it. Next, identify the ending time, and the question the problem is asking.

On your T-Chart, put the starting time on the left hand side, and since we are only working with minutes this time ( We can see that it took Brianna less than 1 hour to complete her homework) write Minutes on the right hand side.

Next, add horizontal lines to your chart, and under the Minutes heading, list minutes in increments of 5, and stop at 55.

Under the left hand column where the starting time is listed, continue listing the time in 5 minute increments until you reach the stopping time (6:50)

When you have reached the stopping time, circle the time and the minutes listed on your T-Chart.

Now you can answer the question. Brianna started her Algebra homework at 6:15. She

finished at 6:50. How long did it take her to complete her homework?

It took Brianna 35 minutes to complete her homework.

The T-Chart Method You can also use the T-Chart method to

figure out elapsed time that includes hours and minutes by using 2 separate T-Charts.

Let’s try this problem:

Ron sat down to draw at 5:10. He drew until 7:25. How long did Ron draw?

The T-Chart Method First, identify your starting time and end

time by circling or highlighting them. Next, identify what question the

problem is asking.

Ron sat down to draw at 5:10. He drew until 7:25. How long did Ron draw?

Next, draw two T-Charts. On the first put the starting time, and Hours at the top.

As before, draw a few horizontal lines down your T-Chart. Under hours, start listing hours starting at 1. You can take a guess at how many hours you will need to list. What do you think?

Next, start listing the appropriate time next to each hour. Stop when you are close to the stopping time, but you have not gone past it.

Circle the time where you should stop. Which time listed below is close to the stopping time, but has not passed it?

*Remember that the stopping time is 7:25.

7:10 is close to the stopping time of 7:25, but is not past it. 8:10 would be too long because it went past the stopping time.

So now we can answer part of the question. Ron drew for 2 hours. But how many minutes?

On your second T-Chart, write the time you reached after counting the hours (7:10) on the left. On the right, write Minutes.

As before, draw horizontal lines down your chart, and list minutes in increments of 5. Take a guess as to how many minutes you will need. If you need to add more minutes, you can always go back to add more.

Under the left hand column, continue listing the times in 5 minute increments until you reach the stopping time. (7:25). When you reach the stopping time, circle it.

Since the stopping time is 7:25, as we earlier identified, we can see that the number of minutes Ron spent drawing was 15 minutes.

We can now answer the entire question:

Ron sat down to draw at 5:10. He drew until 7:25. How long did Ron draw?

Ron drew for 2 hours and 15 minutes.

Let’s try another problem using analog clocks: How much time has elapsed between the

two clocks below?

First, identify the times on each clock:

Next, draw a T-Chart to figure out the time elapsed. Has more than an hour gone by? Then you will need 2 T-Charts.

Set up the first T-Chart labeled with the starting time, and Hours at the top.

Next, draw horizontal lines through your chart and list hours under the Hours column. How many hours do you think you’ll need?

Next, list the appropriate times next to each hour.

Which time is close to the stopping time (4:15) without going past it? Circle it.

Now you can answer the first part of the question. The elapsed time is one hour and…

Now, how many minutes have passed? Draw your T-Chart labeled with the time

you reached after finding the hours, (4:00) and Minutes at the top.

Draw the horizontal lines, and add minutes in 5 minute increments. Keep your stopping time in mind…how many minutes do you need to add?

Finally, add the correct times next to the corresponding minutes. Stop when you reach the ending time (4:15) Circle the time and minutes.

You can now completely answer the question. The elapsed time is:

One hour and 15 minutes

The T-Chart Method Try finding the elapsed times using the

analog clocks on the following slides. Create your own T-Charts to find the answers.

The T-Chart Method You can practice finding elapsed time

further using these websites: http://www.shodor.org/interactivate/activ

ities/ElapsedTime/

http://www.free-training-tutorial.com/telling-time-games.html

http://www.harcourtschool.com/activity/elab2002/grade_3/018.html