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Lessons for Grade 7
Common Core For Grade 7
Examples, videos, and solutions to help Grade 7 students when given Drawing 1 and Drawing 2 (a scale model of Drawing 1 with scale factor), they understand that
Drawing 1 is also a scale model of Drawing 2 and compute the scale factor.
New York State Common Core Math Grade 7, Module 4, Lesson 13
Download worksheets for Grade 7, Module 4, Lesson 13
Lesson 13 Student Outcomes
• Given Drawing 1 and Drawing 2 (a scale model of Drawing 1 with scale factor), students understand that
Drawing 1 is also a scale model of Drawing 2 and compute the scale factor.
• Given three drawings that are scale drawings of each other and two scale factors, students compute the other
related scale factor.
Lesson 13 Summary
To compute the scale factor from one drawing to another, use the representation:
Quantity = percent × whole
where the whole is the length in the actual or original drawing and the quantity is the length in the scale drawing.
If the lengths of the sides are not provided but two scale factors are provided, use the same relationship but use the
scale factors as the whole and quantity instead of the given measurements.
Lesson 13 Classwork
A scale drawing is a reduction of the
actual drawing when the
corresponding lengths of the scale
drawing are
smaller than the lengths
in the actual drawing and when the
scale factor is
less than 100%.
A scale drawing is an enlargement of
the actual drawing when the
corresponding lengths of the scale
drawing are
larger than the lengths in
the actual drawing and when the scale
factor is
greater than 100%.
Opening Exercise
Describe Scale Factor, using percentages, the difference between a reduction and an enlargement.
Use the two drawings below to complete the chart. Calculate the first row (Drawing 1 to Drawing 2) only.
Compare Drawing 2 to Drawing 1. Using the completed work in the first row, make a conjecture (statement) about what
the second row of the chart will be. Justify your conjecture without computing the second row.
Compute the second row of the chart. Was your conjecture proven true? Explain how you know.
Example 1
The scale factor from Drawing 1 to Drawing 2 is 60%. Find the scale factor from Drawing 2 to Drawing 1. Explain your
reasoning.
Example 2
A regular octagon is an eight-sided polygon with side lengths that are all equal. All three octagons are scale drawings of
each other. Use the chart and the side lengths to compute each scale factor as a percent. How can we check our
answers?
Example 3
The scale factor from Drawing 1 to Drawing 2 is 112% and the scale factor from Drawing 1 to
Drawing 3 is 84%. Drawing 2 is also a scale drawing of Drawing 3. Is Drawing 2 a reduction or an
enlargement of Drawing 3? Justify your answer using the scale factor. The drawing is not
necessarily drawn to scale.
Explain how you could use the scale factors from Drawing 1 to Drawing 2 (112%) and from Drawing 2 to Drawing 3
(75%) to show that the scale factor from Drawing 1 to Drawing 3 is 84%.
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