Lesson – Teacher Notes Standard: 7.G.A.1 Solve problems involving scale drawings of geometric figures, including computing actual lengths and areas from a scale drawing and reproducing a scale drawing at a different scale. Section 9.3 – asks students to create scale drawings and convert between measurements. Lesson Focus: The focus is to have students understand and apply scale drawings and scale factors by reproducing scale drawings.(4-2 and 4-5) I can identify corresponding parts of similar geometric figures; and construct a proportion to solve for unknown quantities. Calculator: Yes Literacy/Teaching Strategy: Teammates Consult(4-1); Pairs Check (4-4); Walk and Talk (Closure)

Bell Work

Today you will extend your study of ratios by looking at enlargements and reductions of geometric figures. Think of a copy machine and what it does to a picture when the “enlargement” button is selected. The machine makes every length of the picture larger or smaller by multiplying it by the same number, called the multiplier. That multiplier is also called the scale factor. Multiplier: The number you can multiply by in order to increase or decrease an amount. Scale Factor: A ratio that compares the sizes of the parts of one figure or object to the sizes of the corresponding parts of a similar figure or object.

4-2. Karen wants to try scaling the figure shown below by 50%. What do you think will happen to the figure? a.Sketch the figure shown at right and make a copy of the figure scaled by 50% on your dot paper. What is the same about the copy and the original? What is different? b.Locate at least three pairs of corresponding sides. There are nine in all. Then write and simplify the ratio of each pair of corresponding sides in the order. c.Compare the ratios from each pair of corresponding sides with the scale factor. What do you notice? How do your ratios compare to the scale factor?

4-4. Similar figures are figures that have the same shape but are not necessarily the same size. One characteristic of similar shapes is that ratios of the sides of one figure to the corresponding sides of the other figure are all the same. Another characteristic is that the corresponding angles of the two figures are the same. Patti claims she made a similar copy of each of the original figures shown in parts (a) and (b). For each pair of figures, write and simplify the ratios for each pair of corresponding sides in the order. Compare the ratios. Are the figures similar? That is, did Patti really make a copy?

4-5. Draw a rectangle on dot or graph paper. Then enlarge the sides of the rectangle using a scale factor of 3. a.Compute the perimeter and area of both the new and enlarged rectangles. b.Write and reduce each of the following ratios: c.How does each ratio compare with the scale factor?

Determine the scale factor for each pair of similar figures in problems 1 & 2. 3.A triangle has sides 5, 12, and 13. The triangle was enlarged by a scale factor of 300%. a.What are the lengths of the sides of the new triangle? b.What is the ratio of the perimeter of the new triangle to the perimeter of the original triangle? Practice 1.2.