1. New Unit: STRETCHING AND SHRINKING (SS)
Math CC7/8 – Be Prepared
New Unit: STRETCHING AND SHRINKING (SS)
On Desk:
In your Journal:
Label at top:
Stretching & Shrinking (SS)
Date
handouts
In your Planner:
HW: Stretching and Shrinking (SS) p.16 #5, 9, 10, 13
SD Test back by Friday!
Retakes: Fri, Nov. 2 during class

2. Tasks for Today Warm Up - % of a number SS – Summary of Inv. 1
Begin HW?

3. Warm Up In your journal – 1. Find the given percent of each number
a. 25% of b. 70% of 150

4. Looking Ahead p. 3

5. Looking Ahead p. 4

6. SS Inv. 1.1
SS Inv. 1.2

7. Vocabulary:
Scale drawing - same shape as original, but may be larger or smaller
Image – a copy of the original
Corresponding sides – sides that have the same relative position in similar figures
Corresponding Angles – angles that have the same relative position in similar figures
Similar - ?
By the end of today’s lesson you should have a good definition of similar!

8. Daphne thinks the school copier can make accurate copies in a variety of sizes.
She makes a copy of “Super Sleuth” with the size factor set at 75%.
Then, she makes a copy with a setting of 150%.

9. Corresponding sides have the same relative position in similar figures.

10. The side lengths of the small figure are 0
The side lengths of the small figure are 0.75 (or 75%) times as long as the lengths of the original figure.
The side lengths of the large figure are 1.5 times (or 150%) as large as the lengths of the original figure.

11. Corresponding angles have the same relative position in similar figures.

12. The angle measure remain the same!

13. The perimeters of the small figure are 0
The perimeters of the small figure are 0.75 times as long as the original.
The perimeters of the large figure are 1.5 times as long as the original.

14. (Squares of the copier size factors!)
Each side length in the image is found by multiplying the original length by the same number.
How about the area?
Since the sides are changed by a factor, the area
(a product of the sides: l x w) is changed by a
product of the factor and itself.
(Squares of the copier size factors!)

15. The length and perimeter of the large figure are 1.5 times (or 150%)
75% copy
The length and perimeter of the small figure are 0.75 (or 75%) times as long as the lengths of the original figure.
150% copy
The length and perimeter of the large figure are 1.5 times (or 150%)
as large as the lengths of the original figure.
How do the relationship in the angle comparisons relate to the copier size factors used?
The angle measure remain the same!

16. The area of the smallest figure is a little more than ½ the area of the original .
The area of the largest figure is a little more than double the area of the original.

17. SS p. 14
The length and perimeter comparison factors are the same as the copier size factors.
How about the area?
Since the sides are changed by a factor, the area (a product of the sides: l x w) is changed by a product of the factor and itself.
(Squares of the copier size factors!)

18. The measures of the corresponding angles are the same, but the side lengths may be different.
Each side length in the image is found by multiplying the original length by the same number.

19. New Unit –
Stretching & Shrinking
p. 7

21. p. 13