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Homework Help: Symbolic Question

  1. Aug 29, 2007 #1
    Hi guys, can you help me out with a homework question. I'm stuck and dont know what to do. Question state:

    A spherical balloon with radius r inches has volume V(r) = (4/3)r3. Find a function that represents the amount of air A required to inflate the balloon from a radius of r inches to a radius of r + 1 inches.

    Don't I just replace (r) with (r+1).. ?

    3. The attempt at a solution

    A(r)= (4/3)pi(r+1)^3 ??

    Thanks a lot.
  2. jcsd
  3. Aug 29, 2007 #2
    That would be the amount of air required to inflate a balloon of radius r+1. You want a *difference*.
  4. Aug 29, 2007 #3
    ahh got it :) thank you genneth...
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