This preview shows page 1. Sign up to view the full content.
Unformatted text preview: 11.3 Perimeters & Areas of ~ Figures Figures
p. 677 Thm 11.5 – Areas of ~ Polygons Thm Polygons
• If 2 polygons are ~ with a ratio of If corresponding sides a:b, then the ratio of their areas is a2:b2. their ratio of perimeters = a b scale factor or scale
a 1 2 b ratio of areas = a2 b2 Polygon 1 ~ Polygon 2 Polygon Polygon Ex: The ratio of corresponding Ex The sides of 2 ~ hexagons is 3:2. hexagons
(a.) Find the ratio of their perimeters. 3:2 (b.) Find the ratio of their areas. 9:4 (c.) If the area of the larger hexagon is 45 in2, what is the area of the smaller hexagon? what
45 9 = x 4 9x = 180 x = 20 in2 Ex: A rectangular tablecloth is 60 in X 120 in. A rectangular placemat made from the same cloth is 12 in X 24 in & costs $5. Compare the areas of these objects to find a reasonable cost for the tablecloth. cost 60 12 11 • First, are the rectangles ~? First, ~? = = 120 24 22 Yes Placemat Tablecloth Area: 288 in2 7200 in2 288 Cost: $5 $5 * 25 = $125 $5 Ex: A store sells trampolines that are all Ex store regular hexagons. One trampoline has a side length of 4.5 ft and an area of 52.6 ft2. Find length Find the area of a trampoline whose perimeter is 67.5 ft. 67.5
4.5 ft A = 52.6 ft2 Set up a proportion using the ratio Set of the areas & the ratio of the actual areas. areas. P = 67.5 ft 11.25 ft 4.52 52.6 = 2 11.25 x 20.25 52.6 = 126.5625 x x = 328.75 ft2 Assignment Assignment ...
View Full Document
This note was uploaded on 02/12/2011 for the course MTG 3212 taught by Professor Jackson during the Spring '11 term at University of Florida.
- Spring '11