Crimson Wife Posted July 26, 2011 Share Posted July 26, 2011 DD just asked me this and I'm so not a math person- help! "If you subtract infinity from infinity, would the answer be zero?" I told her that infinity wasn't a specific number because it goes on forever. I don't know if one can subtract infinity from infinity as a result :confused: Quote Link to comment Share on other sites More sharing options...
KAR120C Posted July 26, 2011 Share Posted July 26, 2011 DD just asked me this and I'm so not a math person- help! "If you subtract infinity from infinity, would the answer be zero?" I told her that infinity wasn't a specific number because it goes on forever. I don't know if one can subtract infinity from infinity as a result :confused: Infinity isn't a number, and doesn't follow the rules of numbers. So infinity + infinity is infinity... infinity - infinity could be anything. Quote Link to comment Share on other sites More sharing options...
LetsDoMath Posted July 26, 2011 Share Posted July 26, 2011 Infinity - Infinity is one of the "indeterminate forms". They are most commonly used in the study of limits in Calculus. We just don't know enough to determine what it equals, hence, "indeterminate". :001_smile: Quote Link to comment Share on other sites More sharing options...
Crimson Wife Posted July 26, 2011 Author Share Posted July 26, 2011 Thanks so much! I did take Calculus eons ago so that is vaguely ringing some bells. ;) Quote Link to comment Share on other sites More sharing options...
Critterfixer Posted July 27, 2011 Share Posted July 27, 2011 Not an answer to your question but a great book about the concept of infinity written for kids: The Cat in Numberland. In the book the idea of infinity is presented as the hotel where all the numbers live, where all the rooms are full, but there is always room for one more. Quote Link to comment Share on other sites More sharing options...
joannqn Posted July 27, 2011 Share Posted July 27, 2011 I have no answer but I have heard from a mathematician that teaches gifted kids at the UW that there are different sizes of infinity. From that, I would think that infinity - infinity would not necessarily equal zero. Quote Link to comment Share on other sites More sharing options...
quark Posted July 27, 2011 Share Posted July 27, 2011 "If you subtract infinity from infinity, would the answer be zero?" My son was researching this a while back. Here is a link that may help explain it. This a good forum to ask questions. This one too. Quote Link to comment Share on other sites More sharing options...
wapiti Posted July 27, 2011 Share Posted July 27, 2011 i have no answer but i applaud your efforts to find one. My dc have asked the same or very similar questions and i haven't taken the time and effort to answer correctly :tongue_smilie: Not an answer to your question but a great book about the concept of infinity written for kids: The Cat in Numberland. In the book the idea of infinity is presented as the hotel where all the numbers live, where all the rooms are full, but there is always room for one more. :iagree: My dc enjoyed this Quote Link to comment Share on other sites More sharing options...
LittleIzumi Posted July 27, 2011 Share Posted July 27, 2011 :iagree: My dc enjoyed this Mine too--I still haven't returned it to the library yet :lol:. She thought the cat was silly for not understanding infinity though. :lol: Quote Link to comment Share on other sites More sharing options...
Dana Posted July 27, 2011 Share Posted July 27, 2011 I have no answer but I have heard from a mathematician that teaches gifted kids at the UW that there are different sizes of infinity. From that, I would think that infinity - infinity would not necessarily equal zero. A set can be countably infinite (like the natural numbers, integers, and rational numbers... all are the same size) or uncountably infinite (like the real numbers). I'm off to check out Cat in Numberland now :) Quote Link to comment Share on other sites More sharing options...
Critterfixer Posted July 27, 2011 Share Posted July 27, 2011 She thought the cat was silly for not understanding infinity though. Bless that poor cat! It wasn't the infinity she ran away from as much as the noise and arguments. Quote Link to comment Share on other sites More sharing options...
Crimson Wife Posted July 27, 2011 Author Share Posted July 27, 2011 i have no answer but i applaud your efforts to find one. My dc have asked the same or very similar questions and i haven't taken the time and effort to answer correctly :tongue_smilie: Normally, I ask DH the quant jock these kinds of questions but he was in a meeting so I couldn't call him. I put The Cat in Numberland on hold at our library, thanks for the recommendation! Quote Link to comment Share on other sites More sharing options...
boscopup Posted July 27, 2011 Share Posted July 27, 2011 Normally, I ask DH the quant jock these kinds of questions but he was in a meeting so I couldn't call him. I would have texted DH. :lol: Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.