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bii17

  • 3 years ago

The base diameter and altitude of a right circulAR cone are observed at a certain instant to be 10 and 20 inches respectively. if the lateral area is constant and the base diameter is increasing at a rate of 1 inch per cubic minute, find the rate at ehich the altitude is decreasing

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  1. bii17
    • 3 years ago
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    hmm yes.. he formula is LA = pi*r*L

  2. Gowthaman
    • 3 years ago
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    1 inch per cubic minute .... means what ? i am not understanding ' CUBIC MINUTE'

  3. bii17
    • 3 years ago
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    im sory it's 1 inch per minute

  4. Gowthaman
    • 3 years ago
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    LA = pi*r*L , and here L is slant height

  5. bii17
    • 3 years ago
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    yes...

  6. Gowthaman
    • 3 years ago
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    |dw:1348992383404:dw|

  7. bii17
    • 3 years ago
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    what happn nxt?

  8. Gowthaman
    • 3 years ago
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    is it 1/ sqrt(2) inch/ min

  9. bii17
    • 3 years ago
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    the answer will be 2.25 in per min @Gowthaman

  10. Gowthaman
    • 3 years ago
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    then somewhere i missed, i check once again

  11. bii17
    • 3 years ago
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    okay

  12. Gowthaman
    • 3 years ago
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    but now i got -.25 inch/min

  13. Gowthaman
    • 3 years ago
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    dh/dr =-1/2 (from condition of constant LS area) and dr/dt = 1/2 inch/min (given in the problem) dh/dt = dh/dr x dr/dt = - 1/2 x 1/2 = - 1/4 = -0.25 inch / min

  14. Gowthaman
    • 3 years ago
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    @bii17 ....?

  15. sauravshakya
    • 3 years ago
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    |dw:1348995046484:dw||dw:1348995119250:dw||dw:1348995143495:dw|

  16. sauravshakya
    • 3 years ago
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    |dw:1348995200114:dw|

  17. sauravshakya
    • 3 years ago
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    I hope u can solve it from here...

  18. bii17
    • 3 years ago
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    @sauravshakya hey stil there?

  19. bii17
    • 3 years ago
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    |dw:1349001368987:dw|

  20. bii17
    • 3 years ago
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    @sauravshakya what is that?? i didnt understand those with circle..

  21. sauravshakya
    • 3 years ago
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    That is radius of the cone

  22. sauravshakya
    • 3 years ago
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    Got it?

  23. sauravshakya
    • 3 years ago
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    ALSO,|dw:1349001642850:dw|

  24. bii17
    • 3 years ago
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    @hartnn can u help me in this question?

  25. hartnn
    • 3 years ago
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    which part of saurav's explanation did u not understand?

  26. bii17
    • 3 years ago
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    here.. |dw:1349002226151:dw| i used it but i didnt get the correct answer the answer should be 2.25 @hartnn

  27. hartnn
    • 3 years ago
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    @bii17 i did get it as 2.25. l^2=425, r=5, h=20, dr/dt=2

  28. bii17
    • 3 years ago
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    |dw:1349002789725:dw| i get is 8 @hartnn

  29. hartnn
    • 3 years ago
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    oh sorry, dr/dt = 1/2 and not 2

  30. bii17
    • 3 years ago
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    |dw:1349002976588:dw| my answer is 2.. :( @hartnn can u show me what u did?

  31. hartnn
    • 3 years ago
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    |dw:1349002984911:dw|

  32. hartnn
    • 3 years ago
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    did u get that u missed the -*minus* sign in the beginning ?

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