MR58

G.A November 16, 2008 C Block Stretching and Shrinking

Big Idea: Many things in our world are mathematically similar and we can use this to understand and describe the world around us.

Investigation 4 math reflection pg. 58

1. **How can you decide whether two figures are similar?** You can tell by going through these steps. First find out if the shapes have the same general shape. If they share corresponding angles or side lengths. If they share a ratio of half’s or a scale factor. 2. **What does the scale factor between two similar figures tell you about the relationships between the length and the area measures of the two figures?** Well the scale factor tells us for example if the scale factor is 2. The lengths will have doubled because the scale factor multiplied by the original side length is the new corresponding side length. The area will have quadrupled because the area is the scale factor multiplied by it self. 3. **If the scale factor from a small figure to a large figure is given as a percent, how can you find the side lengths of the large figure from the side lengths of a small figure?** Well you need to know how to change the scale factor to a percent. For example if the percent is 200% the scale factor is 2. Then you multiply the scale factor by the original lengths and you get the new corresponding lengths. 4. **decide whether each pair of rectangles below are simalr. If the rectangles are similar, give the scale facto from the rectangle on the left to the rectangle to the right. If they are not explain why.** A. well they do not have the same general shape. The share corresponding angles but not side lengths, and so with these they do not share a ratio or scale factor. B. They share the same general shape. They have corresponding angles and side lengths, so they have a scale factor which is 3.