Ordinary Differential Equations: radon isotopes and decay

[Julie]

This problem is in my ODE book and I don't see how it's supposed to be solved. It's in the section on separable DE's.


A substance contains two Radon isotopes, 210Rn (with half-life of 2.42 hours) and 211Rn (with half-life 15 hours). At first 20% of the decays come from 211Rn. How long must one wait until 80% of the do so?


Any help would be much appreciated.

 

[Julie]

Nevermind... I've got it figured out

 

[tkhunny]

Generally, it is considered bad form to post in multiple locations - even on different websites.

http://www.sosmath.com/CBB/viewtopic.php?t=32367

We are glad that you managed a reasonable reply that was helpful to you, but if anyone on this site was spending time on your question, you have just wasted the time of a volunteer. You don't want to do that. The world needs volunteers. We don't want to make them angry.

 

[stapel]

The world needs volunteers. We don't want to make them angry.

Heck, twitchy math volunteers might poke you with their protractors! :wink: :lol:

Eliz.

P.S. to Julie: I'm glad you got it figured out!

 

[Julie]

Yes. I know it was somewhat bad form. I was kind of desperate . I did try to post a "nevermind" comment as soon as I had received a reply. Sorry if I inconvenienced anyone.