Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Half life problem

  1. Dec 13, 2009 #1
    1. Half life of a radioactive substance is 13 days. How long for 400 grams to decay to 300 grams? Solve algebraically and show all work. Give both exact answers and the answer rounded to 4 decimal places.



    So I manipulated (1/2)A0=A0e13K to obtain K = ln(1/2)/13

    Where do I go from here?
     
  2. jcsd
  3. Dec 13, 2009 #2

    LCKurtz

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Put your known numbers back in the equation:

    A = A0e(kt)
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook