23 He made the Sea of cast metal, circular in shape, measuring ten cubits from rim to rim and five cubits high. It took a line of thirty cubits[o] to measure around it. 24 Below the rim, gourds encircled it—ten to a cubit. The gourds were cast in two rows in one piece with the Sea. – 1 Kings 7:23-24
I’m not sure what a “Sea” is, but it’s circular (sounds like a cylinder), has a diameter of 10 cubits, and it takes 30 cubits to go around it – the circumference. But we know now that Pi * D = Circumference, …
Continue reading Does the bible say that Pi = 3?
When investing in anything, the investor always wants to know “when do I get my money back?”. This question elicits the following math problem:
Given an interest rate i, when will my principle P double in value (that is, I have made my money back)?
First off, this question is not quite well defined – we are not told how often the interest is compounded (or if it is compounded), but we will work with that.
The rule of 72 is a very convenient little trick for those interested in this rule. The rule states:
Divide 72 by the interest rate. This will …
Continue reading The Rule of 72 (Investing)
With the development of Google Docs (http://docs.google.com/), one has to do word processing on their computer less and less. Working online is usually faster (just a browser to load), and allows your data to be stored in “the cloud”–that is, online rather than on your computer, making the files more secure.
However, for mathematicians there has always been a problem with this–LaTeX. Many of us use LaTeX to write everything. Academic papers, tests and exams, assignments, and even worksheets and letters (my CV was even made in LaTeX). Because of this there has not been much opportunity to switch over to using …
Continue reading Writing Math on the internet!
I had never seen this before–came across a YouTube video explaining it, though the proof is trivial (he doesn’t do it in the video):
So here’s the rule.
Take any big number, say 439239619 (this is a multiple of 7 from how I generated it, but the trick will discover that…in fact, the only prime factors of this particular number are 7 and 13).
The rule is: remove the last number, double it, and subtract the doubled value from whats left of the original. So 9 is the last digit. Double it to get 18. Then subtract 18 from 43923961 (the number formed by …
Continue reading A slick quick way for determining if a number is divisible by 7 (VIDEO)