Area is defined as the amount of space taken up by a two-dimensional shape or surface. Area is measured by taking the total amount of1 unit by 1 unit squares that can fit within a two-dimensional shape or surface.
The area of a circle can be calculated by using the following formula:
A = Area of Circle
π = 3.14 (rounded down) or 22/7
r = radius of the circle
Find the area of a circle whose radius is 12 cm. Use 3.14 as π.
Step 1: Let's plug in the radius and π in the formula. The radius is 12 and π is 3.14.
Step 2: Simplify and write answer in unit squared.
So the area of a circle whose radius is 12 cm is 452.16 cm squared!
Find the area of a circle whose diameter is 28 inches. Let's use 22/7 for π this time around.
Step 1: Find the radius. If the diameter is 28 inches then the radius is 14. it is half the length of the diameter.
Step 2: Let's plug in the radius and π in the formula. The radius is 12 and π is 22/7.
Step 3: Simply and calculate the Area!
So the area of a circle whose diameter is 28 inches is 616 inches squared!
Surface area is the sum of the area of all surfaces on a three-dimensional figure. The best way to think of surface area is if you took a three-dimension figure and flattened out the figure to see all the faces. This is also called a net. Look at the following example using a cylinder:
In the example above, the net of a cylinder consists of two circles and a rectangular shaped figure that is actually curved. You will need to find the area of each part and then add the sum to get the surface area. While the circles use the normal area formula of a circle, the curved rectangular shaped figure uses the circumference formula for its length. Recall, that the area of a rectangle is Area = Length X Height, or A = l x h
Area of the Circles + Area of Curved Rectangle = Surface Area
Find the surface area of cylinder with a radius of 4 inches and a height of 6 inches. Use 3.14 as π
Step 1: Identify the radius and height.
r= 4 inches
h= 6 inches
Step 2: Substitute the values into the formula.
Step 3: Simplify.
SA = 2 ((3.14 * 16) + 2 (3.14) (4) (6)
SA = 2 (3.14 * 16) + 2 (75.36)
SA = 2 (50.24) + 2 (75.36)
SA = 100.48 + 150.72
SA = 251.2 inches squared.
So the surface area of a cylinder with a radius of 4 inches and a height of 6 inches is 251.2 inches squared.
Find the surface area of this cylinder. Use 3.14 as π.
Step 1: Identify the radius and height.
r= 5cm and h=9.5cm
Step 2: Plug in the values into the formula.
Step 3: Simplify.
SA = 2 (3.14 * 25) + (2(3.14)(5))*(9.5)
SA = 2 (3.14 * 25) + 2*(15.7)*(9.5)
SA = 157 + 298.3
SA = 455.3 inches squared
So after adding up the area of the circles and area of the rectangle, the answer came 455.3 inches squared.
Hope you found these helpful!