7th Grade Scale Factor

7th Grade: Introduction to Scale Factor

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​Identifying the Scale Factor between a figure and the scale drawing of that figure.

by Ms. MCBRAYER

​​The Unit Rate as the Scale Factor

What is SCALE FACTOR?

• ​A scale factor in math is the ratio between corresponding measurements of an object and a representation of that object.

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• 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.

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​TYPES OF SCALE DRAWINGS

• If the scale drawing is LARGER than the original, then it is an enlargement.

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• If the scale drawing is SMALLER than the original, then it is a reduction.

​Steps to check for proportionality for scale drawing and original object or picture

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1. ​Create a table and record the lengths of the scale drawing on the table.

2. ​Record the corresponding lengths of the actual/original object or picture on the table.

3. ​Check for constant of proportionality by dividing scale drawing lengths by the original lengths.

Multiple Choice

If the scale factor is less than one, the new figure will be...

• an enlargement

• bigger

• a reduction

• a scale factor

Multiple Choice

If the scale factor is greater than one, the new figure will be...

• an enlargement

• a reduction

• a scale

• not proportional

Multiple Choice

Scale factor of 1/4 is ...

• enlargement

• reduction

Multiple Choice

Scale factor of 4 is ...

• enlargement

• reduction

Multiple Choice

What are corresponding parts?

• parts of a triangle

• another word for the perimeter of a shape

• parts of a square

• lines, points, and angles that are the same value or place on a shape

Multiple Choice

If you want to find the scale factor from one figure to another, which formula should you use?

• old/ new

• drawing / actual

• actual / model

Multiple Choice

What is the scale factor?

• 3

• 1/3

• 5

• 10

Multiple Choice

What is the scale factor from the large triangle to the small triangle?

• 1/2

• 2/3

• 3/4

• 2

Multiple Choice

Are the following similar? Why or why not?

• Yes, the sides are 2 times larger than the original

• No, one pair of corresponding sides are 2 times larger, but the other is the same length

• Yes, because the corresponding sides are the same length

• No, the numbers are even