Results 1 to 3 of 3

Thread: How to derive the rule of 70 from the basic mathematics of exponential growth?

  1. #1 How to derive the rule of 70 from the basic mathematics of exponential growth? 
    Forum Freshman
    Join Date
    Jul 2011
    Hello, everyone! When I studyed demograph, I came across the rule of 70 which is a quich way to calculate the time it takes for a population growing at a specified rate to double its size. But I don't know how the formula derived from the basic mathematics of exponential growth. Can anyone tell me? Many thanks.

    Reply With Quote  


  3. #2  
    Join Date
    Apr 2007
    It's explained here.
    EcoFuture™ Population and Sustainability - Exponential Growth and The Rule of 70
    The Rule of 70 is useful for financial as well as demographic analysis. It states that to find the doubling time of a quantity growing at a given annual percentage rate, divide the percentage number into 70 to obtain the approximate number of years required to double. For example, at a 10% annual growth rate, doubling time is 70 / 10 = 7 years.
    A special case is the doubling time, which is the time when N(t)/N(0) = 2, that is the quantity has doubled from its initial value. At that point

    rt = ln 2 = 0.69

    Reply With Quote  

  4. #3  
    Forum Freshman
    Join Date
    Jul 2011
    Thanks, you help me a lot.
    Reply With Quote  

Similar Threads

  1. how to derive rms(average) fromoeak wattage
    By big red* in forum Electrical and Electronics
    Replies: 1
    Last Post: June 3rd, 2011, 07:33 PM
  2. Exponential equation
    By doctor_cat in forum Mathematics
    Replies: 0
    Last Post: August 5th, 2010, 05:13 AM
  3. exponential differentiation
    By Heinsbergrelatz in forum Mathematics
    Replies: 13
    Last Post: December 2nd, 2009, 11:26 AM
  4. How would one derive this?
    By Gmano in forum Mathematics
    Replies: 12
    Last Post: November 17th, 2009, 04:10 PM
  5. Calculating exponential i
    By DivideByZero in forum Mathematics
    Replies: 3
    Last Post: February 8th, 2008, 06:56 PM
Posting Permissions
  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts