Here’s a cool math trick I saw once.
The number 789789 is a multiple of 13. 789789 = 60573 * 13
The number 123123 is also a multiple 13. 123123 = 9471 * 13
Assertion: Any number of the form ABCABC is a multiple of 13.
The assertion is true. I can prove it. Can you?
I saw an interesting story on Digg today. It was interesting not because of the story, but because I was surprised that others found it interesting. The link was to an article claiming and proving that 0.99… (repeating nines) is equal to 1. That is, they both represent the same number.
This is a tautology that every algebra student should be able to understand.
But the comment thread on the original post is amusing. It starts out with various people claiming it’s not true, and some others showing how the commenters got it wrong. But then it devolves into several thousand comments, many with Math Majors claiming the original post is so far wrong that it’s absurd!
But it is clearly correct, and anyone who thinks otherwise simply doesn’t understand mathematical concepts.
Hey — here’s an easy problem, but with a surprising answer:
What’s are the next two numbers in this series?
142857, 285714, 428571, 571428, 714285, ??????, ??????