CTK Insights

• Pages

27 Mar

Divisibility of N(N+1)(2N+1) by 6

TweetJeffrey Samuelson twitted a question to which I am happy to provide an answer, or two. Question Find an integer N such that N(N+1)(2N+1) is NOT divisible by 6. If no such integer exists, prove why. Since the question is about the properties of a product modulo 6, it seems proper to investigate the dependency […]

26 Mar

Babbage Could Not Pass It By - on Average

TweetWhen Tennyson wrote The Vision of Sin, Babbage read it. After doing so, it is said he wrote the following extraordinary letter to the poet: "In your otherwise beautiful poem, there is a verse which reads: 'Every moment dies a man, Every moment one is born.' "It must be manifest that, were this true, the […]

21 Mar

Happy Purim!

Tweet (Borrowed from http://www.boingboing.net/2011/03/21/how-to-make-a-hamant.html)

20 Mar

The 1089 Prediction Trick and Beyond

TweetSimple mathematics may be rather impressive even on an early developmental level. The "1089 prediction" is one of the better known tricks that may be presented to the 3-4 grade audience. David Acheson describes it thus: Think of a three-digit number. Any three-figure number will do, so long as the first and last figures differ […]

14 Mar

TweetMarch 14 is practically an official π day. Why is that? March is the fourth month of the widely accepted Gregorian calendar and, not incidentally, π ≈ 3.14. There are dissenting voices that claim July 22 as a more appropriate day for the celebration because 22/7 (≈ 3.14286) is a better approximation to the real […]

08 Mar

Inverse Functions

TweetI cannot recollect which book it was but I do remember it was a book by a famous mathematician who wrote in Introduction that to write a book is the best way to learn a new topic. I got this memory flash when reading an article in Mathematics Teacher: Our teachers misled us, but we […]

08 Mar

Real Visual Illusions. Beautiful!

TweetYou have to see it to believe it.

05 Mar

How to Make Your Own Divisibility Criteria

Tweet[mathjax] A decimal integer has the form A divisibility criterion is a procedure, in some sense simpler than straight division, that allows us to determine whether or not number is divisible by another number . For example, is divisible by if and only if the sum of digits is divisible by . For example, is […]