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anonymous

  • 5 years ago

I need help finding the volume of this pentagonal pyramid !!!

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  1. amistre64
    • 5 years ago
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    whatcha stuck on?

  2. anonymous
    • 5 years ago
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    First of all , is there anyway I can draw a picture on here to make it easier?

  3. amistre64
    • 5 years ago
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    lol ... not that I have found

  4. amistre64
    • 5 years ago
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    there is an attach file button here, but it is nnew. might allow you to post a pic tho

  5. anonymous
    • 5 years ago
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    ehh, nahh. i'll just attempt to explain. okay so each side of the base has a length of 16 cm. Then the base has a annulus of 11. And it looks like the height is 36 cm

  6. amistre64
    • 5 years ago
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    annulus; thats a term I aint familiar with.. can you explain it?

  7. anonymous
    • 5 years ago
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    a washer shape

  8. anonymous
    • 5 years ago
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    it's the length from the center of the shape to the middle of the edge of the side

  9. anonymous
    • 5 years ago
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    circular disk with a hole missing from the center

  10. anonymous
    • 5 years ago
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    maybe i'm not using the right term

  11. amistre64
    • 5 years ago
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    ahhh; it looks like we could find the rea of on section of it by using the base and the height and the side length to help us

  12. amistre64
    • 5 years ago
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    my keyboard hates me....

  13. anonymous
    • 5 years ago
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    lol

  14. anonymous
    • 5 years ago
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    so how do we do it

  15. amistre64
    • 5 years ago
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    what methods do we know? is this calculus or something else?

  16. anonymous
    • 5 years ago
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    geometry. . . lol

  17. amistre64
    • 5 years ago
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    so we have a right triangle that forms the base and height, we have a width of ....whatever a side was all the way to 0 at the tip....

  18. anonymous
    • 5 years ago
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    okay. here, can u wait a minute im gonna try to draw a picture of it and attach the file

  19. amistre64
    • 5 years ago
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    http://www.mathsisfun.com/geometry/pentagonal-pyramid.html gives us the volume as: 1/3 [base area] times height

  20. anonymous
    • 5 years ago
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    yes i know that.

  21. amistre64
    • 5 years ago
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    And area of pent is: (length of 1 side)^2 x 1.7

  22. anonymous
    • 5 years ago
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    what is a pent

  23. amistre64
    • 5 years ago
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    Area = 16^2(1.7)(36)/3 is what it looks to be. pentagon

  24. anonymous
    • 5 years ago
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    oh. ha. okay. so you took 16 to the second power , but where did u get 1.7?

  25. anonymous
    • 5 years ago
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  26. amistre64
    • 5 years ago
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    1.7 is what someone smarter than me got when they figured out the formula for the area of a pentagon :) s^2(1.7) = area of pentagon

  27. anonymous
    • 5 years ago
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    the teacher gave us the answers because this a review for a test on monday. and she said the answer should be 5260. i just wanna see how she got there so i can do it on the test

  28. anonymous
    • 5 years ago
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    okay... i think. lol

  29. anonymous
    • 5 years ago
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    i meant 5280cm3. my bad

  30. amistre64
    • 5 years ago
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    I get 5222.4 but is close enough to account for rounding and such

  31. amistre64
    • 5 years ago
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    when we chop of decimals; we skew the answers... so it all depends on how it was calculated..

  32. anonymous
    • 5 years ago
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    yeah. okay and explain to me where you got 36 please

  33. amistre64
    • 5 years ago
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    you said the height was 36. (1/3) (base area) (height) base area = (side^2)(1.7)

  34. anonymous
    • 5 years ago
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    ohhh wow. duhh. sorry. brain fart lol

  35. amistre64
    • 5 years ago
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    :)

  36. amistre64
    • 5 years ago
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    do you remember that you asked about the volume of a pentagonal pyramid :) time passed and we got to here :)

  37. anonymous
    • 5 years ago
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    ha , yes. okay that works.

  38. anonymous
    • 5 years ago
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    do you have time for some more questions?

  39. amistre64
    • 5 years ago
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    fraid not, library closes in 10 minutes and my internet goes with it... but have a great day :)

  40. anonymous
    • 5 years ago
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    okay thank you! you too!

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