Since radius is not a multiple of 7, we can use π ≈ 3.14. Since the top of the biscuit is in the shape of a circle, we can use area of circle formula to find area of the top of the biscuit. Find the area of the top of the biscuit once it is cut. Using the formula for circumference, we haveĪ biscuit recipe calls for the dough to be rolled out and circles to be cut from the dough. įrom the diagram shown above, we can see that the diameter of the circle is

So, the circumference of the wheel is 66 inches.įind the diameter, radius, circumference and area of the circle shown below. The diameter of a car wheel is 21 inches. So, the circumference of the region watered by the sprinkler is about 88 feet. Find the circumference of the region watered by the sprinkler. The measurements of area use units such as square centimeters (cm 2), square meters(m 2), and so on.Īn irrigation sprinkler waters a circular region with a radius of 14 feet. of RTV.The measurements of perimeter use units such as centimeters, meters, kilometers, inches, feet, yards, and miles. Then you would take 37.68 - 26.45 to give you a total of 11.23 cubic inches.ġ1.23 cubic inches x 21 grams per cubic inch = 236 grams of RTV needed.Īnd then if you want to calculate that into lbs.

Now using the same formula subtract the cubic inches of your part.Įxample: The part is 3.5' diameter (1.75' radius) by 2.75' high.ġ.75' x 1.75' (radius squared) x 3.14 (pi) x 2.75' (height) = 26.45 cubic inches. Formula for a Round Mold: Pi x Radius (squared) x Height Example: The diameter of a mold is 4' (the radius would then be half of that being 2') and the height is 3'.Ģ' x 2' (radius squared) x 3.14 (pi) x 3 (height) = 37.68 cubic inches. Then you would take 72 - 42 to give you a total of 30 cubic inches.ģ0 cubic inches x 21 grams per cubic inch = 630 grams of RTV needed.Īnd then if you want to calculate that into lbs. Now using the same formula subtract the cubic inches (volume) of your part.Įxample: Your part is 8' x 3.5' x 1.5' = 42 cubic inches. Formula for a Square/Rectangle Mold: Length x Width x Height Example: You have a mold box that needs to be filled up 9' x 4' x 2' = 72 cubic inches in order to completly cover your original/part. Note: There are 21 grams per cubic inch of Silicone Rubber. Amount of RTV Needed for Making a Silicone Rubber Mold

21 inch radius what is the area