02/12/2012 — Another Permutation Day!

Today we celebrate our second Permutation Day of the year!  I call days like today permutation days because the digits of the day and month can be rearranged to form the year.

We enjoyed our first permutation day of 2012 just 21 days ago.  Exactly three weeks apart!  That seems unusual.  I also wonder “How close could two permutation days be?”

Celebrate Permutation Day by mixing things up!  Try doing things in a different order today.  Just remember, for some operations, order definitely matters!

01/22/2012 — Happy Permutation Day!

Today we celebrate our first Permutation Day of the new year!  I call days like today permutation days because the digits of the day and month can be rearranged to form the year.

We enjoyed several Permutation Days in 2011.  In addition to predicting future dates, an interesting question would be “Which year has the most Permutation Days?”

In honor of today, I recommend changing the order in which you do things!

2011: A Prime Year

The year 2011 was quite remarkable, numerically speaking at the very least.  Here are some interesting facts about the number 2011.

First and foremost, 2011 is prime.  The last prime-numbered year was 2003 and the next will be 2017 (thank you WolframAlpha!).

What is more interesting is that 2011 is a prime that is the sum of eleven consecutive prime numbers!  This was first pointed out by @mathematicsprof.

Afterwards, it was pointed out by @republicofmath that 2011 is expressible as another sum of consecutive primes!

When will we see such a numerically interesting year again?

Worst Discount Ever

This has to be some kind of record for smallest difference between sale price and regular price.

Using the standard formula for percent change

we find the difference in sale price and original price to be

\frac{119.99 - 119.00} {119.99} \approx 0.00825

That’s a 0.8% discount!  Was this really worth printing up a “SALE!” sign?

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