Finding the Radius of a PipeDate: 1/28/96 at 1:30:40 From: Anonymous Subject: Geometry A pipe has become bent and is no longer round. In order for me to correct the problem, I must build a brace to go around the pipe and true it up. However, until I can determine the radius of the pipe, a brace cannot be built. How do you determine the radius of a circle when all you know is the circumference ? Date: 3/4/96 at 21:53:30 From: Doctor Jodi Subject: Re: Geometry Hi there! If you had the radius and wanted to find the circumference, you'd use the formula: circumference = pi * 2 * radius (you may have also seen this written as pi * Diameter, since the Diameter is twice the radius). Now, since you have the circumference and want the radius, we need to get the radius alone on one side of the equal sign. We can do this by using INVERSE OPERATIONS. If this makes sense, you can skip this next part ------------------------------------------------ Addition and subtraction are inverses; so are multiplication and division. For example, 3 * 5 = 15 If we multiply each side by 2, both sides will still be equal. 2 * (3 * 5) = 2 * 15 we see that 2 * (3 * 5) = 30 2 * (15) = 30 30 = 30 ------------------------------------------------------------- We can do the same thing with the formula above, circumference = pi * 2 * radius We want to solve for the radius--that is, we want the radius alone on one side of the = sign. so first, we divide through by 2 circumference /2 = pi * 2 * radius / 2 which also equals circumference /2 = pi * radius Next we divide through by pi: (circumference / 2)/pi = radius which can be rewritten circumference /(2 * pi) = radius Pi is a really cool number that doesn't end; one rough approximation is 3.14 Your calculator will have a closer approximation. -Doctor Jodi, The Math Forum |
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