area and surface area of 2d shapesunit 22.pptx

Area

1. What is Area?

2. What is Area? Area  is the amount of space  inside  a shape. It is measured in square units.   If you place a shape on a grid, the area is the number of squares that can fit inside the shape.

3. For a rectangle, you could count the number of squares to find the area. For example, the rectangle shown covers 12 squares so the area is 12 square units.

4. Instead of counting squares, you can also use a formula to find the area of a rectangle.   The formula for the area of a rectangle is Area = length x width. For the rectangle above, we could have also multiplied 4 x 3 to find the area. 4 3

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6. What would happen if we cut a rectangle in half to form a triangle?   What would the new area be? The area of the rectangle is 12 square units. If the rectangle has been cut in half to form two equal triangles, then each triangle must have 1/2 the area of the rectangle. This means we can take 1/2 of 12 to find the area of the triangle, so the area is 6 square units.

7. How Do You Find the Area of a Triangle? There is a formula we can use to find the area of a triangle. It's similar to the formula for the area of a rectangle, except it uses base and height instead of length and width. A triangle takes up half as much space as a rectangle, so there is a 1/2 in the formula.

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9. What if the triangle doesn't look like the one drawn?   Sometimes the height isn't one of the sides of the triangle. The base and height of a triangle are always perpendicular to each other, so look for the box that marks the 90 degree angle.   × ×

10. What if the triangle doesn't look like the one drawn?   Sometimes the height isn't one of the sides of the triangle. The base and height of a triangle are always perpendicular to each other, so look for the box that marks the 90 degree angle.  

11. Step 1: Identify the base and height.  The base and height must be at a 90 degree angle. This means the  base = 12  and  height = 10 × × × ×

12. The surface area is the area calculated for the three-dimensional object. As the three-dimensional object is made up of 2D faces, the surface area is the sum of the areas of all the faces of the figure. Cubes, cuboids,

13. Cuboid  Surface Area of Cuboid To calculate the surface area of the cube, let’s open it up like in the figure given below. Now the figure shows the flattened cuboid. It has 6 rectangles which correspond to the six faces of the cuboid.

14. For the surface area of the cube, we need to find out the total area of all the 6 faces.  surface area of the cube