Things to Learn

  • Recognize that the enlarged or reduced distances in a scale drawing are proportional to the corresponding distances in the original picture.
  • Recognize the scale factor to be the constant of proportionality.
  • Given a picture or description of geometric figures, make a scale drawing with a given scale factor.
    Steps to check for proportionality for scale drawing and original object or picture:

  1. Record the lengths of the scale drawing on the table.
  2. Record the corresponding lengths on the actual object or picture on the table.
  3. Check for the constant of proportionality.
  4. The constant of proportionality is the scale factor of a scaled picture, drawing, or 3D model.
    Key Idea:

  • The scale factor can be calculated from the ratio of any length in the scale drawing to its corresponding length in the actual picture. The scale factor corresponds to the unit rate and the constant of proportionality.

Scaling by factors greater than 1 enlarges the segment, and scaling by factors less than 1 reduces the segment.

Picture Scaling

Exercise and Practice

The Park Swimming Pool