tag:blogger.com,1999:blog-8208757670243748671.post4300376546895056117..comments2023-09-22T10:59:04.474-07:00Comments on Redneck Math: Casting Out Mathematical DemonsBobby Wintershttp://www.blogger.com/profile/13590953639823213422noreply@blogger.comBlogger4125tag:blogger.com,1999:blog-8208757670243748671.post-51993296815616208582015-01-27T16:49:34.566-08:002015-01-27T16:49:34.566-08:00I love your blog. I just wanted to comment that I ...I love your blog. I just wanted to comment that I think 6+8=14 not 17 - though neither is divisible by 9. Lisahttps://www.blogger.com/profile/13163585803665511746noreply@blogger.comtag:blogger.com,1999:blog-8208757670243748671.post-10837912410639621652014-06-25T10:02:23.883-07:002014-06-25T10:02:23.883-07:00I worked out a test for divisibility by seven duri...I worked out a test for divisibility by seven during a trip to the bathroom in fifth grade, though it took me another ten years to figure out why it worked, and another five to generalize it into a method for creating divisibility tests for all integers relatively prime to 10. I guess it's true what they say about mathematicians getting older.<br /><br />The one for seven goes like this: Chop the last digit off the number, double it, and subtract it from what's left of the number. If the result is divisible by 7, so is the original. For instance, the CAPTCHA here wants to me identify number on apartment 105. 10-2*5=0, and 0 is divisible by 7, so 105 is also divisible by 7.<br /><br />Alternatively, one could chop off the last digit, multiply it by 5, and add it to what's left. If the result is divisible by 7, so was the original. So, for the example before 10+5*5=35 which is divisible by 7, so 105 is also.<br /><br />This method is generalizable, but I'll give you a hint to do it yourself: the first method is related to the fact that 21 is a multiple of 7, and the second one is related to the fact that 49 is a multiple of 7.Quintopiahttps://www.blogger.com/profile/11935053984682797775noreply@blogger.comtag:blogger.com,1999:blog-8208757670243748671.post-65787135431105727562014-06-25T10:00:51.480-07:002014-06-25T10:00:51.480-07:00This comment has been removed by the author.Quintopiahttps://www.blogger.com/profile/11935053984682797775noreply@blogger.comtag:blogger.com,1999:blog-8208757670243748671.post-42887338302767484002014-05-10T03:19:34.971-07:002014-05-10T03:19:34.971-07:00If any one worry about Math then don’t worry about...If any one worry about Math then don’t worry about it, we learn Math with different very easy tools and methods. We have Online free Math Website for kids – to learn & Practice math skills. 2nd Grade, 3rd Grade,6th Grade kids for Add, Subtract, Multiply,<a href="http://www.ipracticemath.com/math-practice" rel="nofollow">Math Division</a>, Algebra, Word problems, Worksheets and more which you want<br />Anonymoushttps://www.blogger.com/profile/09596543922736382314noreply@blogger.com