TIL: In a numeric system of base 'x', 10 is always equal to 'x'. Binary 10 = 2, Decimal 10 = 10, Hex 10 = 16.

13    07 Jul 2016 06:24 by u/rwbj

Courtesy of tweet.

Obvious when you think about it... but how many people have thought about it?

17 comments

8

Since 10x is by definition x1+0 this is indeed very obvious. This also implies that it is possible to write any number in such a way that it ends in a zero. Now, the more interesting thing to think about is, given an integer n, what is the maximum number of zeros you can make it end with by picking an appropriate basis?

2

Ooh, nice puzzle. I think the number of zeroes is equal to logk x for the smallest integer k which produces an integer logarithm.

There's probably a nicer way to phrase that.

3

The easier way to phrase is is "the highest power in the prime factorisation." For example: 28=7⋅22, so the highest power is 2. Indeed, 28 in binary is 11100. The highest number of ending zeros also always occurs in a prime number basis. Although that number does not need to be unique to one basis. For example 36=33⋅22, so it ends in two zeros in both basis two (3610=1001002) and basis three (3610=11003).

0

Nice! Thank you for a puzzle on my day off.

1

Hahah, you've gotta refine the question a bit. The answer as posed is infinite as you can have arbitrarily small fractional bases. For a integral base you can give another cheat answer. Base 1 with a symbol of 0 such that 51 = 00000. An integral > 1 base is an interesting and ostensibly tricky one though!

1

Well, yes. Integers only, and integer bases only.

2

Not always. You're making unstated assumptions. There are many varied number systems other than those with which people are generally familiar. Here's one example. https://en.wikipedia.org/wiki/Bijective_numeration

2

Spot the pure maths junkie. :P

2

https://archive.is/tPA4t :

Jesse Howell on Twitter: "@notch @kkearns Ah... I get it now. I like Base 10 (binary) and base 10 (hexidecimal), but I use base 10 (decimal) most often."

This has been an automated message.

1

Looks good!

1

https://archive.is/tPA4t : Jesse Howell on Twitter: "@notch @kkearns Ah... I get it now. I like Base 10 (binary) and base 10 (hexidecimal), but I use base 10 (decimal) most often."

This has been an automated message.

3

Nice bot. Might be better to use the standard quote system with '>' instead of the code block since there's no word wrap in code blocks.

0

Can't use quotes on a line that already contains text, >like this.

3

I was just thinking something like this:

https://archive.is/tPA4t :

Jesse Howell on Twitter: "@notch @kkearns Ah... I get it now. I like Base 10 (binary) and base 10 (hexidecimal), but I use base 10 (decimal) most often."

This has been an automated message.

2

Best I could do would be to toss the text onto a new line as a quote, the bot is pulling that text from the title since it mainly targets articles.

0

No shit, the values of the digits, from left to right, are multiples of xn, xn-1, xn-2, . . . , x2, x1, x0. To answer your question, anyone who has taken a single computer science class has thought about it.

0

Yes, but it's a realisation the first time.