7.6 The student will use proportions to solve practical problems, which may include scale drawings, that contain rational numbers (whole numbers, fractions, and decimals) and percents.

Directions 1

  • Drag the squares until the side length of the second square is twice as long as the first.
  • Compare the perimeter of the first square to that of the second.
  • Do the same comparison for the areas. Is there a relationship? If so, what is it?
  • Does it have anything to do with the scale factor of two that we used?

Directions 2

  • You are given a rectangle with a width of 2 and a length of 3. Find the area of this rectangle.
  • Now multiply each side length by 3. What do you predict the new perimeter will be? New area?
  • Check your prediction using the figures provided. Try using the squares with a scale factor of 3.

Directions 3

  • You are given a figure that has perimeter P. You apply a scale factor of n to this figure to create a larger similar figure. Write an expression for the perimeter of this new figure.
  • In general, what is the rule to find the area of a similar figure if the original area, A, and scale factor, s, are known?

Hands-On Activities

Other Web Sites

  • Numberpower There are notes on how find the percent of a number and when the student scrolls down, there is a Flash movie.
  • Learn Alberta View an interactive video on proportions.
  • ExploreLearning Teachers have to assign the Beam to Moon to their classes.
  • Larson´s Software Students need to be enrolled by their teachers. Click on the Ratios, Rates, and Proportions, then click on Solving Proportions.

Lesson 2-4: Using Proportions to Solve Practical Problems


See the directions on the right.

Sorry, the GeoGebra Applet could not be started. Please make sure that Java 1.4.2 (or later) is installed and activated. (click here to install Java now)
Created using GeoGebra.