document.write( "Question 831122: A cylindrical jar of radius 3cm contains water to depth of 5cm. The water is then poured at a steady rate into an inverted conical container with its axis vertical. After t seconds, the depth of water in this container is x cm and the volume, V ml, of water that has been transferred is given by V= 1/3 (pie)(x)(x)(x).
\n" ); document.write( "Given that all the water is transferred in 3 seconds,find
\n" ); document.write( "a) dv/dt in terms of pie
\n" ); document.write( "b) the rate at which c is increasing at the moment when x= 2.5
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Algebra.Com's Answer #501353 by KMST(5328)\"\" \"About 
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The volume in that cylindrical jar, calculated as \"pi%2Aradius%5E2%2Aheight\" ,
\n" ); document.write( "is \"pi%2A%283cm%29%5E2%2A%285cm%29=pi%2A45cm%5E3=pi%2A45mL\" .
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\n" ); document.write( "a) If that volume is transferred at a steady rate in \"3\" minutes, the average and constant rate is
\n" ); document.write( "\"dV%2Fdt=pi%2A45mL%2F%223+min%22=15pi\"\"mL%2Fmin\" (or \"15pi\"\"cm%5E3%2Fmin\" ).
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\n" ); document.write( "b) Since there is no \"c\" mentioned in the problem before part b),
\n" ); document.write( "I assume that the question for part b) was
\n" ); document.write( "to find the rate (maybe called c) at which the water level is increasing in the inverted conical container,
\n" ); document.write( "when that water level there is \"x=2.5cm\" .
\n" ); document.write( "That rate would be \"dx%2Fdt\" .
\n" ); document.write( "At a constant rate of \"15pi\"\"mL%2Fmin\" , at \"t\" minutes the volume in the inverted conical container would be \"V=15pi%2At\"
\n" ); document.write( "We also know that \"V=%281%2F3%29%2Api%2Ax%5E3\" .
\n" ); document.write( "We can use those two equations to find \"dx%2Fdt\" and the value of \"dx%2Fdt\" when \"x=2.5cm\" .
\n" ); document.write( "I believe the easiest way to find the value of \"dx%2Fdt\" when \"x=2.5cm\" is to consider that if \"V\" is a function of \"x\" and \"x\" is a function of \"t\" ,
\n" ); document.write( "\"dV%2Fdt=%28dV%2Fdx%29%2A%28dx%2Fdt%29\" .
\n" ); document.write( "We know that \"dV%2Fdt=15pi\" (for all values of \"t\" ),
\n" ); document.write( "and from \"V=%281%2F3%29%2Api%2Ax%5E3\" we calculate \"dV%2Fdx=pi%2Ax%5E2\" .
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\n" ); document.write( "When \"x=2.5cm\" , \"dV%2Fdx=pi%2A%282.5cm%29%5E2\" ,
\n" ); document.write( "so at that point
\n" ); document.write( "\"15pi\"\"cm%5E3%2Fmin=pi%2A%282.5cm%29%5E2%2A%28dx%2Fdt%29\"
\n" ); document.write( "\"15cm%5E3%2Fmin=2.5%5E2cm%5E2%2A%28dx%2Fdt%29\"
\n" ); document.write( "\"dx%2Fdt=15%2F2.5%5E2\"\"cm%2Fmin\"
\n" ); document.write( "\"dx%2Fdt=2.45\"\"cm%2Fmin\" at the point when \"x=2.5cm\" .
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\n" ); document.write( "That does not give me a general expression for \"dx%2Fdt\" as a function of \"t\" , but I do not believe the problem asked for that.
\n" ); document.write( "However, just for fun, let's try to solve that way.
\n" ); document.write( "With your excuse, I will skip writting the units this time.
\n" ); document.write( "\"system%28V=15pi%2At%2CV=%281%2F3%29%2Api%2Ax%5E3%29\" --> \"15pi%2At=%281%2F3%29%2Api%2Ax%5E3\" --> \"15t=%281%2F3%29x%5E3\" --> \"45t=x%5E3\" --> \"x=%2845t%29%5E%221+%2F+3%22\"
\n" ); document.write( "\"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2At%5E%22-+2+%2F+3%22\"
\n" ); document.write( "\"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2Ft%5E%222+%2F+3%22\"
\n" ); document.write( "That still does not look pretty, but I cannot make improve it too much, so I let it be.
\n" ); document.write( "When \"x=2.5\" , \"45t=2.5%5E3\" --> \"t=2.5%5E3%2F45\"
\n" ); document.write( "Substituting into \"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2At%5E%22-+2+%2F+3%22\" we get
\n" ); document.write( "\"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2A%282.5%5E3%2F45%29%5E%22-+2+%2F+3%22\"
\n" ); document.write( "\"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2A%2845%2F2.5%5E3%29%5E%222+%2F+3%22\"
\n" ); document.write( "\"dx%2Fdt=45%5E%221+%2F+3%22%2A%281%2F3%29%2A45%5E%222+%2F+3%22%2F2.5%5E2\"
\n" ); document.write( "\"dx%2Fdt=45%2A%281%2F3%29%2F2.5%5E2\"
\n" ); document.write( "\"dx%2Fdt=15%2F2.5%5E2\"
\n" ); document.write( "\"dx%2Fdt=2.45\"
\n" ); document.write( "So we get to the same result, and we have \"dx%2Fdt\" as a function of \"t\" as a bonus, in exchange for a bit more arithmetic work.
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