STRETCHING AND SHRINKING UNIT SS SS 2 3
- Slides: 16
STRETCHING AND SHRINKING UNIT (SS) SS 2. 3 Mouthing Off and Nosing Around – Scale Factor Learning Target: I can find the relationships between scale factor, perimeter, and area in similar figures. Homework: Day 5 SS: Watch the Pre-Teaching EDpuzzle on REP-TILES and TAKE NOTES on p. 13. Warm-up: 8 + (16 – 12) + (2 x – 5) = –(3)² + 9(7 x – 2) =
HW p. 11 review and Vocab Tool Kit:
HW Review p. 11: side same angles The _______________ is the number scale factor that the side lengths of one figure can be multiplied by to give the corresponding lengths of the other figure. greater less
image 6 = = original 2 image 3 1/3 image original 3 1/3 2 1 = 6 3 3
image 6 1 = = original 12 2 ½ ½ 2 2 times bigger than the smaller triangle. The larger triangle is ____ image 12 2 = = = original 6 1 2
Use LS 2. 3 to complete p. 12 in the packet: Teacher Note: It will save time to give half the class the rectangles (Section A, 1 -4) to work with and half the class the triangles (Section B, 1 -4. ) Then have team report out their findings.
Rectangles (mouths) J, L, and N are similar. All angles are right angles, or the same size, so you only need to check the side lengths.
Triangles (noses) O, R, and S are similar to each other.
Scale factors (small to large): Scale factors (large to small): O to R = 2 R to O = ½ O to S = 3 S to O is 1/3 R to S = 3/2 Perimeters: O= R= S= Area: O=1 R=4 S=9 S to R is 2/3 Reciprocals!
Yes! The area of the larger triangle is the “square of the scale factor” times the area of the smaller triangle. The scale factor from O to S is 3 and nine O fit into triangle S. (3 x 3 = 9 = ) Scale factor is 3
The perimeter of the larger rectangle = scale factor x the perimeter of the smaller rectangle. (You have increased all sides by the same factor!) The area of the larger rectangle = “square of the scale factor” x the area of the smaller rectangle.
NO! Using a constant scale factor to stretch or shrink sides does not change the angle size.
SS 2. 3 Mouthing Off and Nosing Around – Scale Factor Did I reach my Learning Target? I can find the relationships between scale factor, perimeter, and area in similar figures. Homework: Day 5 SS: Watch the Pre-Teaching EDpuzzle on REP-TILES and TAKE NOTES on p. 13.
