Tuesday, April 30, 2013

Area of a rectangle

Area of a rectangle

The formula for area of a rectangle is b*h (base times height)

In a rectangle the opposite sides are congruent so if you the measure of one side then you also know the measure of the opposite side.   

 Please watch the video to see each problem worked out

You Tube Area of a Rectangle

Problem 1. Find the area of a rectangle with a base of 10 units and a height of 8 units.

 

Step 1. Plug the numbers into the formula b*h 

 

8 * 10 =80 units squared

 

Next, let’s look at one more challenging. 

 

Problem 2. Find the base of a rectangle with an area of 100 units and a height of 5 units.

 

Step 1. Write the formula for the area of a rectangle Area= b*h

 

Step 2. Plug in what you know 100 = b * 5

 

Step 3 Divide each side by 5   100/5= b/5  

 

Step 4. 20 =b and b = the base of the rectangle

 

Problem 3. Find the area of a rectangle with a diagonal of 15 units and a side of 9 units.

 

Step 1. Plug in what you know A = b * 9

 

Step 2. The diagonal divides the rectangle into a right triangle. You can use the Pythagorean Theorem to find the base. 

A = 9 c= 15 b=your unknown (see picture below)

 

 

 area rectangle

9^2+ b^2= 15^2 

81+ b^2=225

b^2=144  

b=√144 

b = 12

 

 

Step 3. Use your area formula of a rectangle Area = b*h

Area = 12 * 9 = 108 u^2