Fourth grade students are developmentally ready to move beyond simple sequencing tasks to understand elapsed time. You can build upon their previous knowledge of seconds, minutes and hours to show them that "elapsed" means the amount of time that passes from one point to the next, such as from the 8:00 school start time to the day's end at 3:00.

## Use Addition and Subtraction

During fourth grade, students learn how to use operations to solve time interval equations, according to the Common Core State Standards Initiative. Set up a series of simple word problems that require students to use addition and subtraction. Start with addition and then create a few equations the students can relate to. For example, "Recess starts at 1:00 p.m. and lasts for 15 minutes. What time is recess over?" The students must add 15 to 1:00 to get the 1:15 end point. Use subtraction and set up a word problem such as, "Your leg of a relay race starts at 1:01 and 5 seconds. You pass on the baton to another runner at 1:06 and 10 seconds. How much time did it take you to run your leg of the race?" The students must subtract the minutes and seconds to show how much time has elapsed.

## Set Up Multiplication and Division Equations

Multiplication and division allows you to teach elapsed time as portions or fractions. Give your students a story problem such as, "Billy spent 15 minutes cleaning his room. Shana spent twice as long cleaning hers. How much time did it take Shana?" The students must multiply 15 by two to get 30. Next, ask them what part of an hour is 30. For example, "What portion of an hour went by as Shana cleaned?" They must recall that an hour is 60 minutes, divide it by 30 to get two and explain that Shana spent one-half of an hour cleaning.

## Write a Time Journal

Help your students understand how time passes during the course of a day by using a time journal. A time journal details the start and end points of each activity during a set period of time. Assign a specific amount of time such as one weekend day. This encourages your students to explore what they do during the day and how time elapses through activities and events. Send home a notebook with each student over the weekend. Include a letter to the parents that explains the assignment and asks parents to help their children keep track of the time. The students will write down what they are doing and will write the start and stop times, as well. For example, the student may write, "7:00 wake-up, 7:01 start watching cartoons, 7:17 stop watching cartoons, 7:18 start eating breakfast, 7:27 finish breakfast, 7:28 take cereal bowl to mom, 7:29 get dressed, 7:35 finish dressing," and so on. At school, the students can calculate how much time they spent on each activity to see how time passes over the course of an entire day.

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## Estimate a Length of Time

Help your students understand that a minute doesn't always feel the same. Time elapsing during an engaging activity may seem to pass more quickly than time during a dull activity. Set up a comparison experiment to contrast how one minute can feel between the two experiments. Set a stop watch for 60 seconds. Say, "start" and have the students stare at the wall or at their blank desks for the 60 seconds. When they believe that a minute has elapsed, ask them to raise their hands. It's likely that they will raise their hands well before the 60-second mark. Try the same activity during recess or during a more engaging activity. For example, when your students are engrossed in an art project, start timing and ask them to tell you when 60 seconds has passed. The time will seem to pass more quickly, because they are engaged in an enjoyable activity, and you may need to clue them in to the fact that an entire minute has passed.

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