June 2007Area and TilingsSlide 3 Finding the Area of a Geometric Shape The area of a triangle is half that of a rectangle that encloses it Area = Width Height Rectangle Triangle Area = Base Height / 2 Triangle Circle Area = ( /4) Diameter 2 = Radius 2 Square Area = Side 2 The area of a circle is about 80% of the square that encloses it
June 2007Area and TilingsSlide 4 On a sturdy piece of cardboard, draw a 4 6 rectangle Activity 1: The Area of a Triangle Place thumbtacks or pushpins into the two lower corners Put a rubber band around the two thumbtacks or pushpins and stretch it so that it forms a triangle, with the top vertex at the upper left corner of the rectangle. Is it obvious that the area of the triangle is half the area of the rectangle? Now, slowly move the rubber band so that the top vertex shifts to the right along the rectangles top edge. What happens to the area of the triangle as you move the top vertex?
June 2007Area and TilingsSlide 5 Method 1: Approximate the irregular shape by a regular one Measuring the Area of an Irregular Shape Method 2: Cover with 1 1 tiles; count whole tiles and half of broken ones
June 2007Area and TilingsSlide 6 Draw a large irregular area on a piece of cardboard or construction paper Activity 2: Tiling an Area with Square Tiles 15 or more Draw a straight line through the middle of the area in any direction Use square post-it notes as your tiles Place tiles, one by one, on one side of the straight line that you have drawn, taking care that the tiles are aligned and there is no gap between them (real tilers actually leave a gap between tiles where they will pour the grout) Now, moving up and down from the row of tiles placed next to the line, finish tiling of the area, leaving spaces only where whole tiles would not fit; make sure the tile sides are perfectly aligned, with no gap between them Cut tiles to appropriate shapes to fill the irregular areas at the edges Taking your tiles to be 1 1, estimate the area of the irregular shape in ft 2
June 2007Area and TilingsSlide 7 Any shape with right angles and side lengths that are integers can be tiled using 1 1 tiles. Simple Tilings with Nonsquare Tiles Some, but not all, shapes can be tiled using 1 2 tiles To be completely covered with 1 2 tiles, a shapes area must be even, but this is not enough
June 2007Area and TilingsSlide 8 A chess board, or any rectangle with at least one even side, can be completely covered with 1 2 tiles Covering a Chess Board with 1 2 Tiles What if we remove two squares at opposite corners?
June 2007Area and TilingsSlide 9 Tile a 4 6 rectangle using 1 2 tiles of two different colors. Try to find at least two tilings that look nice (have interesting color patterns) Activity 3: Tiling with 1 2 Tiles
June 2007Area and TilingsSlide 10 Tile a 4 6 rectangle using L-shaped tiles that cover three squares. Is there more than one way to do this? Activity 4: Tiling with L-Shaped Tiles
June 2007Area and TilingsSlide 11 Challenge: Try to come up with other ways of mixing 1 2 and 1 1 tiles Some Possible 1 2 Tiling Patterns Mixed with 1 x 1
June 2007Area and TilingsSlide 12 Some Irregular Tiling Patterns Challenge: Try to come up with other interesting irregular tiling patterns
June 2007Area and TilingsSlide 13 Triangular, Hexagonal, and Other Patterns These mixed hexagonal and pentagonal tiles dont quite cover a flat surface area but...
June 2007Area and TilingsSlide 14 Cut out a number of hexagonal and triangular tiles with sides of equal length (use paper of different colors) and use them to tile a square area Activity 5: Mixed Triangular and Hexagonal Tiles
June 2007Area and TilingsSlide 15 Two-Color Tiles
June 2007Area and TilingsSlide 16 Multicolor and Patterned Tiles