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anonymous

  • one year ago

*Area of the base equals* a)8 pi square units b)16 pi square units c) 64 pi square units

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  1. anonymous
    • one year ago
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    https://suwannee.owschools.com/media/g_geo_2013/8/group100.gif

  2. anonymous
    • one year ago
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    @jordanwhitehead

  3. anonymous
    • one year ago
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    @elic2k15

  4. anonymous
    • one year ago
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    @UsukiDoll

  5. anonymous
    • one year ago
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    @math1234

  6. UsukiDoll
    • one year ago
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    I'm juggling one question back in forth.. so if I'm slow to reply sorry in advanced. Anyway we are given a cylinder |dw:1435669876398:dw|

  7. anonymous
    • one year ago
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    It's okay

  8. UsukiDoll
    • one year ago
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    the formula for area of the base of a cylinder is A = pi(r^2)

  9. anonymous
    • one year ago
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    Okay. But every time I put it into the calculator it shows: either 39.4384 or 50.24

  10. UsukiDoll
    • one year ago
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    I know.. we don't calculate the pi part.. leave it as is. so if r = 4 what is r^2?

  11. UsukiDoll
    • one year ago
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    looking at the choices... I think it doesn't want you to calculate the pi.. it's just finding the r and then squaring it

  12. anonymous
    • one year ago
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    Well then it's just 16

  13. anonymous
    • one year ago
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    So it's B?

  14. UsukiDoll
    • one year ago
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    A=pi(4^2) A=pi(16) =16 pi yeah

  15. anonymous
    • one year ago
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    Thanks. So would it be about the same thing for this problem?

  16. anonymous
    • one year ago
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    A cylinder has a volume of 245 pi cubic units and a height of 5 units. The diameter of the cylinder is a) 7 units b) 14 units c) 49 units

  17. UsukiDoll
    • one year ago
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    I think we need the diameter of the cylinder formula.

  18. UsukiDoll
    • one year ago
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    yeah we need a different formula for that.

  19. UsukiDoll
    • one year ago
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    \[\large V = \pi r^2h\]

  20. UsukiDoll
    • one year ago
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    so given height is 5 units volume is 245 pi cubic units . Looks like we're solve for r and then the diameter is twice the radius (d=2r) .. AHA! We need to find the radius first

  21. anonymous
    • one year ago
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    Yes

  22. UsukiDoll
    • one year ago
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    ok let V = 245, and h = 5

  23. anonymous
    • one year ago
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    V r h = � or 2 =

  24. anonymous
    • one year ago
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    Well that didn't come out right

  25. anonymous
    • one year ago
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    :(

  26. UsukiDoll
    • one year ago
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    \[\large 245 = \pi r^2(5)\]

  27. anonymous
    • one year ago
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    What's "large"?

  28. UsukiDoll
    • one year ago
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    that's to make the font large

  29. UsukiDoll
    • one year ago
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    oh are you trying to use the equation tool? right click show math as -> tex command and it will have this code or text you can copy and paste. And then click on the equation tool and paste.

  30. anonymous
    • one year ago
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    Oh

  31. UsukiDoll
    • one year ago
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    so we are solving for r that would mean that r needs to be by itself

  32. UsukiDoll
    • one year ago
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    our first goal is to have r^2 by itself .. and then afterwards we can take the square root

  33. anonymous
    • one year ago
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    \[V = \pi r2h\]

  34. anonymous
    • one year ago
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    r is squared

  35. UsukiDoll
    • one year ago
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    yeah it should have that ^ that carrot sign

  36. UsukiDoll
    • one year ago
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    \[\large V = \pi r^2h \]

  37. UsukiDoll
    • one year ago
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    anyway back to this \[\large 245 = \pi r^2(5) \] we need r^2 by itself so what do we need to do?

  38. UsukiDoll
    • one year ago
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    should we add both sides? subtract both sides? multiply both sides? or.. divide both sides by 5pi

  39. anonymous
    • one year ago
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    divide both sides by 5 pi

  40. UsukiDoll
    • one year ago
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    yes. \[\large \frac{245}{5 \pi} = r^2\]

  41. UsukiDoll
    • one year ago
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    now we take the square root of both sides

  42. anonymous
    • one year ago
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    So 49 = ?

  43. anonymous
    • one year ago
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    Umm

  44. UsukiDoll
    • one year ago
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    we're not done.. we need to take the square root on both sides

  45. UsukiDoll
    • one year ago
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    UH OH! I need to refresh my screen is crazy

  46. anonymous
    • one year ago
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    kk

  47. anonymous
    • one year ago
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    Go ahead

  48. anonymous
    • one year ago
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    I neded to digest a little

  49. UsukiDoll
    • one year ago
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    ok so taking the square root of both sides \[\large \sqrt{ \frac{245}{5 \pi} }= \sqrt{r^2}\] what is the square root of r^2

  50. UsukiDoll
    • one year ago
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    we need to take the square root of r^2 so we can have r

  51. UsukiDoll
    • one year ago
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    then once we have our r we can get the diameter. which is d =2r

  52. anonymous
    • one year ago
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    r=2.5

  53. UsukiDoll
    • one year ago
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    that's not a choice for answers that would've yielded d = 5.. that's not right

  54. anonymous
    • one year ago
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    No wait. 5 was the height not the diameter

  55. anonymous
    • one year ago
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    mY BAD SRY

  56. UsukiDoll
    • one year ago
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    wait a minute we are solving for r.

  57. UsukiDoll
    • one year ago
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    we have already plugged in V and h... now we need to take the square root of both sides. We're almost there

  58. anonymous
    • one year ago
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    I was thinking that the diameter is 7

  59. anonymous
    • one year ago
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    cus 7 squared is 49

  60. UsukiDoll
    • one year ago
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    \[\large \sqrt{ \frac{245}{5 \pi} }= \sqrt{r^2} \] becomes ??? what is the square root of r^2

  61. anonymous
    • one year ago
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    49 times 3.14 = 153.86

  62. anonymous
    • one year ago
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    Umm

  63. anonymous
    • one year ago
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    7

  64. UsukiDoll
    • one year ago
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    once we find r we can find the diameter which is d = 2r

  65. UsukiDoll
    • one year ago
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    What? ok no substituting we are solving for r we need the square root of r^2 .

  66. UsukiDoll
    • one year ago
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    I want an r by itself

  67. UsukiDoll
    • one year ago
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    we have square rooted both sides.. which is correct. Now we just need the square root of r^2 Then we have this \[\[\[\large \sqrt{ \frac{245}{5 \pi} }= r\] \]

  68. UsukiDoll
    • one year ago
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    now the diameter is d=2r so d = 2( That whole square root)

  69. UsukiDoll
    • one year ago
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    \[\large \sqrt{r^2} \rightarrow r^{\frac{2}{2}} \rightarrow r^1 \rightarrow r \]

  70. UsukiDoll
    • one year ago
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    so now our \[d=2(\sqrt{\frac{245}{5 \pi}})\]

  71. UsukiDoll
    • one year ago
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    so we just need 245 divided by 5 pi... take the square root of that result and multiply by 2

  72. anonymous
    • one year ago
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    7.9

  73. UsukiDoll
    • one year ago
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    yes. so our diameter is 7.9 kind of a dangerous number because we can round up to 8

  74. UsukiDoll
    • one year ago
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    7 units would be the closest to the answer.. though the real answer is 7.9

  75. anonymous
    • one year ago
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    Okay. Look I'm sorry if I aggravated you. It's been a long couple of weeks and I'm really tired

  76. anonymous
    • one year ago
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    Thanks for the help. I really appreciate it

  77. UsukiDoll
    • one year ago
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    it's ok ... I'm also tired.. in fact it's almost 4 in the morning. I need zzz's before my dad get suspicious again.

  78. UsukiDoll
    • one year ago
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    that's why I had my latex wrong... r to the first power is just r if it was r^0 that would've been 1. But I should always take the advice of never do math while tired.

  79. anonymous
    • one year ago
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    Yeah I can connect with that

  80. UsukiDoll
    • one year ago
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    I have to go sleep. night

  81. anonymous
    • one year ago
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    Really. Wow it's 9:55 AM here

  82. anonymous
    • one year ago
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    well alright

  83. anonymous
    • one year ago
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    I live in Florida btw

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