Tag Archives: contest

2017: Leonardo, Fibonacci and Fermat Numbers: It’s Not So Complicated.

In my previous post we had a math competition. Let me remind you of the task:

Using +, -, x, ÷ and (), make the row of numbers from 10 to 1 equal 2017.

That was an easy task, which got more complicated.

How about 9 to 1 with arithmetic equalling 2017? 8 to 1? 7 to 1? And down to just 1?

Before I could say ‘What January blues when you’ve got arithmetic in your life!?!’ I had answers from people in our fan club streaming in! And some of them (remember, there are different possibilities to get the same answer of 2017) were so wonderfully interesting, while others were so interestingly not-quite-elegant enough, that, well, I just had to share some of them with you…

Read on: A real math indulgent…

2017: Prime Numbers, Factorials, Primorials, Derangements: It’s Complicated.

As many will already know, the number 2017 is a prime number; that is, it can be divided without a remainder only by itself and 1. Must say, the theory of prime numbers is a wholly interesting one and an extremely useful one too, as any cryptographer will tell you :).

But today I’ll be writing about something different. See, based on the fact that 2017 is prime – or ‘simple’ – many, myself included, are anticipating a simple, straightforward and calm year 2017, especially since 2016 was a bit of a rotter. Let me show you why.

Like I said, prime numbers are those that can only be divided by themselves and 1 without leaving a remainder. Non-prime numbers are called composite numbers, incidentally.

Turns out that 2016 is not only a composite number but a very composite number! It has a whole eight divisors. Grab a calculator your smartphone and test it for yourself:
2016 = 2 * 2 * 2 * 2 * 2 * 3 * 3 * 7

Whoah! Even the quantity of divisors is anything but simple, since 8 = 2 * 2 * 2.

So what about other years? Was 1917, the year of the Russian Revolution, a ‘prime’ year, for example? No, it wasn’t. 1917 = 3 * 3 * 3 * 71. Just four divisors, but they’re kinda poignant – and prophetic of nothing much good.

So what about other very prime/simple years, and other very non-prime/non-simple ones? Ok, let’s narrow this down a bit to 1980 through present day…

Prime/simple years:
1987
1993
1997
1999
2003
2011

And in the near future there are a few more prime/simples:
2027
2029

(eek, that’s a lot of non-simple years until then)

The most non-prime/non-simple years were:
1984 = 2 * 2 * 2 * 2 * 2 * 2 * 31 (seven divisors)
2000 = 2 * 2 * 2 * 2 * 5 * 5 * 5   (also seven)

There were six divisors in 1980, and there’ll be six in 2025. All other years can be called semi-prime/semi-simple.

But I digress…

Now, in the popular British mathematical journal The Guardian :), readers were recently teased with a… brain teaser. In the blanks between the sequence of figures 10 9 8 7 6 5 4 3 2 1 you need to add arithmetic symbols (+, -, x, ÷, (),) – as many as you like – so as to get the number (year) 2017.

For example, if you add arithmetic signs as follows you get 817:
10 * 9 * (8 + 7 – 6) * (5 – 4) + 3 * 2 + 1 = 817

But how do you add arithmetic to get 2017?
10?9?8?7?6?5?4?3?2?1 = 2017

Come on, have a go!

As for me, in nine minutes I got the equation to equal 2017 by kinda wonky arithmetic (I made the ‘3’ and ‘2’ = ’32’!); then, in around 15 or 20 minutes I got the answer in a proper way without bending the rules. I say ‘a’ way: there are different ways of getting to 2017!

So, tried it yet?

Ok, let’s make it harder: Now take away the 10:
9  8  7  6  5  4  3  2  1 = 2017

Read on: How to make 2017 out of 1?…

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