Today we celebrate the final Permutation Day of the year! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.
Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!
How much blue do you see? One-fourteenth is certainly an odd number to see around town.
Today we celebrate a Derangement Day! Usually I call a day like today a permutation day because the digits of the day and month can be rearranged to form the year, but there’s something extra special about today’s date:
The numbers of the month and day are a derangement of the year: that is, they are a permutation of the digits of the year in which no digit remains in its original place!
Derangements pop up in some interesting places, and are connected to many rich mathematical ideas. The question “How many derangements of n objects are there?” is a fun and classic application of the principle of inclusion-exclusion. Derangements also figure in to some calculations of e and rook polynomials.
So enjoy Derangement Day! Today, it’s ok to be totally out of order.
Today we celebrate the third Permutation Day of the year! I call days like today permutation days because the digits of the day and the month can be rearranged to form the year.
Celebrate Permutation Day by mixing things up! Try doing things in a different order today. Just remember, for some operations, order definitely matters!
We have been having fun with our SumBlox, which recently arrived. The number blocks are cleverly designed so that the height of each is proportional to its value.
Here we have the ten block
and here we have multiple mathematical ways to achieve the same height as the ten block: five + five, three + seven, and nine + one.
So far, playing with SumBlox seems like a fun way to build number sense and explore basic properties of addition like equivalence and commutativity. But there does seem to be one problem: I think they got the height of this block wrong!
