Area of rectangles and rectangular shapes. Concrete case of the distributive property (3.MD.7.c). скачать в хорошем качестве

Area of rectangles and rectangular shapes. Concrete case of the distributive property (3.MD.7.c).

In this 3rd grade math lesson, I show that AREA has to do with covering a shape with little squares. In other words, area of any shape is always measured in squares (square units). Area of rectangles can be found by multiplication. In my example rectangle, we count the rows and columns, and then write a multiplication to find the area (5 x 3 = 15 squares). We also write multiplications and addition to find the area of a two-part rectangular area. Next, I use a two-part rectangle tiled with squares to show a connection between multiplication and addition -- in reality, the distributive property. In symbols, the area of a rectangle with whole-number side lengths a and b + c is the sum of a × b and a × c. However, we don't use symbols in the lesson - just actual rectangles with side lengths that are small whole numbers. This concept (area model) does prepare students to understand the distributive property later on. This lesson ties in with the Common Core Standard 3.MD.7, specifically 3.MD.7.a, 3.MD.7.b, 3.MD.7.c, and 3.MD.7.d. See also my workbook Math Mammoth Early Geometry at http://www.mathmammoth.com/early_geom...