Elapsed Time Two

Shodor > Interactivate > Lessons > Elapsed Time Two


In this lesson, students will learn about time and how to calculate an ending time given the starting time and elapsed time.


Upon completion of this lesson, students will:

  • be able to calculate ending time given the starting and elapsed time

Standards Addressed:

Student Prerequisites

  • Arithmetic: Students must be able to:
    • complete simple addition
  • Technological: Students must be able to:
    • perform basic mouse manipulations such as point, click, and drag
    • use a browser for experimenting with the activities

Teacher Preparation

Students will need:

  • access to a browser
  • paper and pencil

Key Terms

additionThe operation, or process, of calculating the sum of two numbers or quantities
elapsed timeA period of time that has passed, usually between a given starting time and ending time

Lesson Outline

  1. Focus and Review

    Review what the students learned in the previous lesson:

    • Elapsed time is the time between a starting and ending time.
    • When adding or subtracting time, you must always be careful to count only 60 minutes in each hour. You must also be careful with a.m. and p.m. times and switching between the two.

  2. Objectives

    Let the students know what they will be doing and learning today. Say something like this:

    • Today, class, we are going to learn how to calculate an ending time.
    • We are going to use the computers to do this, but please do not turn your computers on until I ask you to. I want to show you a little about this activity first.

  3. Teacher Input

    Lead the students in a discussion about how to calculate ending time.

  4. Guided Practice

    • Have the students draw starting times and elapsed times on their Elapsed Time Two Record Sheet. Then instruct them to calculate the elapsed time.
    • Open your browser to the Elapsed Time Two applet. Explain to the students how to work the applet.

  5. Independent Practice

    • Have students answer 10 problems on their own.
    • Have the students answer the Exploration Questions while working with the applet.

  6. Closure

    • Discuss as a class what the students discovered while answering the exploration questions.

Alternate Outline

If there is only one computer, this lesson can be modified in the following ways:

  • The teacher can prepare problems by giving students various starting and ending times. The students can then discuss methods for finding elapsed time.
  • Students who need additional help can use the applet after completing the problems on paper.

Suggested Follow-Up

Students who become comfortable working with elapsed time might be ready to move onto the Clock Arithmetic applet and the Modular Arithmetic lesson.

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