stretching1studyguide
Stretching and Shrinking
Investigation 1: Enlarging and Reducing
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Make sure you can do the following by the assessment of investigation 1:
- measure and identify types of angles
- measure lines
- compute area, perimeter, and circumference (if formulas are given)
- convert percents to decimals
- understand the term corresponding
Goals of the Investigation:
Students should understand that when enlarging or reducing figures:
- the shape stays the same
- the corresponding angles measure the same
- the segments will either increase or decrease
- the perimeter will either increase or decrease
- the area increases or decreases (at a different rate)
OPTIONAL ANSWER KEY: parallelogram grows 140%
What do you notice about the shapes?
The shapes have stayed the same eventhough the image is 140% of the original.
What do you notice about the corresponding angles?
The corresponding angles all have the same measures eventhough the image is 140% of the original.
What happened to the lengths?
The lengths of the segments all grow 40% or are 140% of the original.
What has happened to the perimeter?
The image perimeter is 140% of the original or it is 40% larger than the original.
What has happened to the area?
The area also increases, but it is more than 40%. Area doesn't change at the same rate as the lengths or perimeter.
Dodd Middle School 2007-2008