Happy New Year, Happy 2015, Happy 11111011111 which is, of course, 2015 in binary, Base 2.*

And its a palindrome, which, as you know, I like.

Speaking of palindromes, Monday is not only the first day back at school, its also the first **palindromic date** of the year:

5 1 15

and we won’t see another **palindromic date** until October when we get one a month for the last three months of the year:

5 10 15

5 11 15

5 12 15

The 6th October is an interesting date as it is a **Triangle Day**:

6 10 15

as 6, 10, 15 are three consecutive triangle numbers.

**(American) Pi Day**, 3.14, is particularly good this year (remember, Americans write the month, then the day) as it becomes:

3.14 15

which is Pi to the first 4 decimal places. An if you want to be really precise, make a note of what you are do at 9.26 and 53 seconds as it will be:

3.14 15 9 26 53

Pi to nine decimal places.

As ever, there are always a few **‘n’ days**, the first of which is 5 October:

5 10 15 or 5n

some other **‘n’ days** are:

1 8 15 or 7n – 6

3 9 15 or 6n – 3

7 11 15 or 4n + 3

9 12 15 or 3n + 6

I’m sure you spotted a pattern in those dates – perhaps your pupils could too?

With a little poetic licence, we have **30 – 5n** day on the 2nd May (2 5 2015) Geddit?!

And of course, every year we have **Approximate Pi day** on 22/7 and the **Root of All Evil Day** on 25th August.

With so many exciting dates, there’s plenty to look forward to in 11111011111, sorry, 2015.

**Happy New Year!**

*I always think that it is a shame that different number bases is not part of the curriculum. Perhaps that’s a post for another day.

I converted 2015 into binary using this site.

## 5 Comments

How I wish I could calculate pi (3.141592)

What is n , please?

Joy x x

Hi Joy

“n” stands for any number, and we typically use it when describing a number sequence, so first of all we make n = 1, then n= 2, n = 3 and so on.

So, for example, when we have 4n + 3 when n=1 we do 4×1 + 3 = 7, when n=2 4×2 +3 = 11 etc. so 4n + 3 is the general form for the sequence 7, 11, 15 …

Hope that makes some sense!

Happy New Year.

So does that mean that with your 5 10 15 or 5n that n is 6? I always thought I was quite good at maths, but that stuff has thrown me. (I did only get an O level – in 1964!)

No, for 5, 10, 15 n is 1, then 2 then 3 etc. 5n describes, or is the rule for creating, the series of numbers 5, 10, 15 etc. Then next number in this pattern would be 20, made when n is 4 as 5 x 4 = 20.

5n could be written as 5xn (as lazy mathematicians, we often leave out a times sign).

5×1 = 5 is the first number in the sequence, when n= 1

5×2 = 10 is the second number in the sequence, when n = 2

5×3 = 15 is the third number in the sequence, when n = 3 etc.

OK, I think I understand. Thanks