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-   -   An aluminum plate is:outer radius 12inches and inner radius 5 inches. Using 3.14 as a (https://www.askmehelpdesk.com/showthread.php?t=495160)

  • Aug 5, 2010, 08:05 AM
    jessez72
    An aluminum plate is:outer radius 12inches and inner radius 5 inches. Using 3.14 as a
    An aluminum plate is:outer radius 12 inches, inner radius 5 inches. Use 3.14 as an approximate value: How many square inches in the plate? And If the cost to construct the plate is $5.50 per square inch, what is the construction cost?
  • Aug 5, 2010, 08:19 AM
    KISS

    I think they used the wrong word here. I think it should be called a ring or a washer.
  • Aug 5, 2010, 11:02 AM
    ebaines

    The area of a circular plate is found using . To find the area of a circular plate with a circular hole in it, find the area of a solid plate using the outer radius, then subtract the area of the hole. Then multiply the resulting area by the cost per square inch.

    Post back with what you get as an answer, and we'll check it for you.
  • Aug 5, 2010, 11:32 AM
    jessez72
    Quote:

    Originally Posted by ebaines View Post
    the area of a circular plate is found using . To find the area of a circular plate with a circular hole in it, find the area of a solid plate using the outer radius, then subtract the area of the hole. Then multiply the resulting area by the cost per square inch.

    Post back with what you get as an answer, and we'll check it for you.

    lost!
  • Aug 5, 2010, 11:46 AM
    ebaines

    OK, let's start slow. What's the area of a circle of radius 12 inches? I bet you can find an example of this calculation in your text book...
  • Aug 5, 2010, 12:53 PM
    jessez72
    Quote:

    Originally Posted by ebaines View Post
    OK, let's start slow. What's the area of a circle of radius 12 inches? I bet you can find an example of this calculation in your text book ...

    3.14 12x5
    12-5=7
  • Aug 5, 2010, 12:56 PM
    jessez72
    Quote:

    Originally Posted by jessez72 View Post
    3.14 12x5
    12-5=7

    seven square inches?
    7x5.50=$38.50??
  • Aug 5, 2010, 12:57 PM
    Unknown008

    That is not it.

    The area of the larger circle is given by the formula ebaines gave you, that is:



    So, the larger area is:

    Now, find the smaller area.

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