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    (Original post by Mr M)
    Back to the start before you made the mistake of thinking the cylinder was closed?

    Edit: Do you think it is closed at one end and open at the other? The question is a bit ambiguous or have you paraphrased?
    hey, i posted a pic of my working and I got to the point robbie got to

    now I am asked to show that V= pi/2 (192r-r^3)

    any ideas?:P
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    (Original post by madfish)
    for the next part I am asked to show that V= pi/2 (192r-r^3)

    any ideas?
    Find the volume for an open ended cylinder in terms h and r, but you have h so it will purely just be r's an pi's. I can't quite recall the formula, my c2 differentiation is my weakest area (mins, max peace of cake but real life applications I'm terrible at)
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    (Original post by madfish)
    hey, i posted a pic of my working and I got to the point robbie got to

    now I am asked to show that V= pi/2 (192r-r^3)

    any ideas?:P
    Also have you followed Mr M's instruction, my algebra was just to show you an example of how to manipulate an equation algebraically
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    (Original post by Robbie242)
    Find the volume for an open ended cylinder in terms h and r, but you have h so it will purely just be r's an pi's. I can't quite recall the formula, my c2 differentiation is my weakest area (mins, max peace of cake but real life applications I'm terrible at)
    the formula for the volume is the same with any cylinder, it is pir^h but I cannot get it in the form the are looking
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    (Original post by madfish)
    the formula for the volume is the same with any cylinder, it is pir^h but I cannot get it in the form the are looking
    Volume of a cylinder={\pi}r^2h Your H may be wrong perhaps
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    (Original post by Mr M)
    Try it yourself and you will see you still have R on both sides of your equation.
    I am stuck at this part..
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    hhelp with this would be great, thanks
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    (Original post by madfish)
    I am stuck at this part..
    So it turns out you were right then, the cylinder was open at one end!

    This is like a guessing game!

    That does simplify to the expression you require.
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    (Original post by Mr M)
    So it turns out you were right then, the cylinder was open at one end!

    This is like a guessing game!

    That does simplify to the expression you require.
    I am unsure of how to get it into that form, i have tried relentlessly to get it, but i cant

    my basic maths is awful :L thanks for your help, really really appreciated!
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    (Original post by madfish)
    I am stuck at this part..
    H=\frac{192{\pi}-{\pi}r^2}{2\pi r} -> (cancel {\pi}) H=\frac{192-r^2}{2r} ->(split fractions) H=\frac{192}{2r}-\frac{r^2}{2r} For fraction one simply divide by two so \frac{192}{2r}=\frac{96}{r} then for the second one use the rule \frac{a^m}{a^n}=a^{m-n}
    and that should get you this equation simplified and treat a as r, I don't want to give you the entire answer
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    (Original post by madfish)
    I am unsure of how to get it into that form, i have tried relentlessly to get it, but i cant

    my basic maths is awful :L thanks for your help, really really appreciated!
    Ok right at outset you were told to cancel \pi on the top and bottom of your expression for h. That might help you.
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    (Original post by Robbie242)
    H=\frac{192{\pi}-{\pi}r^2}{2\pi r} -> (cancel {\pi}) H=\frac{192-r^2}{2r} ->(split fractions) H=\frac{192}{2r}-\frac{r^2}{2r} For fraction one simply divide by two so \frac{192}{2r}=\frac{96}{r} then for the second one use the rule \frac{a^m}{a^n}=a^{m-n}
    and that should get you this equation simplified and treat a as r, I don't want to give you the entire answer
    the second = r/2 then?
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    (Original post by madfish)
    the second = r/2 then?
    precisely, do not forget the minus from ,earlier though
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    (Original post by Robbie242)
    precisely, do not forget the minus from ,earlier though
    but sure this cannot be used in showing that that expression equals the area as we do not have 192 in it?

    GOT IT!!!!!!!!!!!!!!!!! thanks robbie dude
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    (Original post by madfish)
    but sure this cannot be used in showing that that expression equals the area as we do not have 192 in it?

    GOT IT!!!!!!!!!!!!!!!!! thanks robbie dude
    No problem!
 
 
 
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