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anonymous

  • one year ago

Find the exact circumference of a circle with an area equal to 36 sq. in. a. 12 pi b. 18 pi c. 324 pi

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  1. anonymous
    • one year ago
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    12 Pi

  2. anonymous
    • one year ago
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    How do you find the radius from this info? Or lack thereof

  3. jim_thompson5910
    • one year ago
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    A = pi*r^2 36 = 3.14*r^2 solve for r to get r = ??? once you know the value of r, you can find the circumference C C = 2*pi*r

  4. anonymous
    • one year ago
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    But how do you find R? Thats where Im stuck

  5. anonymous
    • one year ago
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    the question wants the circumference function in pi... so we can get the relation

  6. jim_thompson5910
    • one year ago
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    did you divide both sides of 36 = 3.14*r^2 by 3.14 ?

  7. anonymous
    • one year ago
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    No.

  8. jim_thompson5910
    • one year ago
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    what do you get when you do so

  9. anonymous
    • one year ago
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    Well 36/3.14 is 11.46

  10. jim_thompson5910
    • one year ago
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    now if r^2 = 11.46, then what must r be?

  11. anonymous
    • one year ago
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    What does ^ mean?

  12. jim_thompson5910
    • one year ago
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    r^2 means r squared

  13. jim_thompson5910
    • one year ago
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    r^2 = r*r

  14. jim_thompson5910
    • one year ago
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    for example, 5^2 = 5*5 = 25

  15. anonymous
    • one year ago
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    So multiply 11.46 by 11.46?

  16. anonymous
    • one year ago
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    Wait, no. 5.73 multiplies by 5.73?

  17. anonymous
    • one year ago
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    Multiplied?

  18. jim_thompson5910
    • one year ago
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    some number, multiplied by itself, gives 11.46

  19. jim_thompson5910
    • one year ago
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    to find this number, you take the square root of 11.46

  20. jim_thompson5910
    • one year ago
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    it turns out that sqrt(11.46) = 3.385 roughly which means 3.385*3.385 = 11.458225, pretty close to 11.46

  21. anonymous
    • one year ago
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    So then i have 36=3.14*3.38^2?

  22. jim_thompson5910
    • one year ago
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    now use that r value to find the circumference C use C = 2*pi*r

  23. anonymous
    • one year ago
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    So two times pi times 3.38?

  24. jim_thompson5910
    • one year ago
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    2 times pi times 3.38

  25. jim_thompson5910
    • one year ago
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    oh sry didn't see your two, nvm

  26. jim_thompson5910
    • one year ago
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    yes you are correct

  27. anonymous
    • one year ago
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    21.23 is what I got.

  28. jim_thompson5910
    • one year ago
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    Question: does the original "36" given in the problem also have a "pi" attached to it?

  29. anonymous
    • one year ago
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    Yes

  30. jim_thompson5910
    • one year ago
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    ok so that changes things a bit

  31. anonymous
    • one year ago
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    Sorry.

  32. jim_thompson5910
    • one year ago
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    if the area is A = 36pi, then A = pi*r^2 36pi = pi*r^2 36 = r^2 ... the pi terms cancel if r^2 = 36, then r = ??

  33. anonymous
    • one year ago
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    6?

  34. jim_thompson5910
    • one year ago
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    yes, then you plug that into C = 2*pi*r

  35. anonymous
    • one year ago
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    37.69?

  36. jim_thompson5910
    • one year ago
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    notice how each answer has a 'pi' in it so ignore the pi for now compute 2*r and then tack on 'pi' at the end

  37. jim_thompson5910
    • one year ago
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    example: if r = 7, then 2*pi*r = 14pi

  38. anonymous
    • one year ago
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    Im still getting the same thing.

  39. jim_thompson5910
    • one year ago
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    you should get 12pi

  40. anonymous
    • one year ago
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    2 times R which is 6 means 12. Then 12*pi. The answer I'm getting is still 37.69

  41. jim_thompson5910
    • one year ago
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    2*r = 2*6 = 12

  42. jim_thompson5910
    • one year ago
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    you leave it as 12pi

  43. anonymous
    • one year ago
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    OH! Okay.

  44. anonymous
    • one year ago
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    Thank you so much! Sorry I am so bad at this!

  45. jim_thompson5910
    • one year ago
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    whenever you see the key term "exact" that means to leave the 'pi's as they are

  46. jim_thompson5910
    • one year ago
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    you did good

  47. anonymous
    • one year ago
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    Oh. Sounds good. Thank you that means a lot!

  48. jim_thompson5910
    • one year ago
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    you're welcome

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