Education Technology

What's My Ratio?

Published on 06/09/2008

Activity Overview

Students use linear measurement and calculators to investigate proportionality and determine the constant ratio between similar figures.

Before the Activity

  • See the attached PDF file for detailed instructions for this activity
  • Print student activity sheets pages 92 - 93 from the attached PDF file for your class
  • During the Activity

    Distribute the pages to the class.

    Follow the activity procedures:

  • Draw a picture on centimeter grid paper
  • Decide to either increase or decrease the size of the picture, predict the dimensions in the increased or decreased version, and discuss reasoning
  • Draw the increased or decreased picture on grid paper, keeping the picture's original shape, to test the predictions
  • Discuss the use of ratio (comparing the measurements of corresponding parts) to describe how the picture has been increased or decreased
  • Divide students into groups
  • Give each group an interesting picture and a reduced or enlarged copy of the same picture
  • Ask each group to measure several pairs of corresponding parts on the two pictures, record their data on the recording sheet, and make some conclusions about copies of pictures
  • After the Activity

  • Review student results
  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary