# Why decimal?

1. Nov 27, 2009

### trini

Ok so i was thinking about it recently, why do we use the decimal system as opposed to other counting systems in math? is there some distinct advantage in using decimal over other systems?

2. Nov 27, 2009

### hamster143

Because we have ten fingers.

3. Nov 27, 2009

### trini

that's all? that seems quite illogical as there appear to me to be many more irrational decimal numbers than there are in, say, base 6 number systems(senary)

4. Nov 27, 2009

### rasmhop

There are exactly the same number of irrational numbers in base 6. In fact whether a number is irrational or not does not depend on the base. The choice isn't that important for most uses so we just stick with what's popular. Base 2, 8 and 16 are also pretty popular bases (especially in computer science).

5. Nov 27, 2009

### hamster143

The existing numeral system coalesced more than a 1000 years ago, at the time when numbers were mostly used for finger counting. Finger counting application makes systems which are based on numbers 5 and 10 preferable over all others. Once a convention like that is universally accepted, it's very hard to replace it, even in the face of major advantages of other conventions (the use of imperial units like foot and pound in the US and the UK is a good example).

6. Nov 27, 2009

### DaveC426913

You think we count in base 10 because we are too proud and bloody-headed to change?

:tongue2:

7. Nov 27, 2009

### mathman

The United States can't even switch to using the metric system for weights and measures. It would take a major miracle to change our ordinary number system to ther than decimal.

8. Nov 27, 2009

### trini

sorry perhaps i should have said recurring numbers, as for example, 1/3 to base 6 = 0.2

to compare systems, i look at the number of finite vs. infinite answers within a range, so for example, in a case of 1/n, where n is an integer, base 6 carries less infinite answers than base 10 over wide ranges.

9. Nov 27, 2009

### trini

yes i understand your point, and it would be very difficult to see such a thing happening without some MAJOR application, especially given the intuitiveness of the finger based system in teaching, as you pointed out though, it is used where useful(eg computer science.)

Another question, does changing base affect the shapes of functions in any way? for example, in the case of plotting a number series, would the series have a different shape if plotted in a system other than decimal?

10. Nov 27, 2009

### hamster143

It's easy to see that you can write down more fractions with, say, two base 10 digits than with two base 6 digits.

11. Nov 27, 2009

### trini

why? you can write the same amount of fractions, except, for eg, instead of saying 1/9 (decimal) you would say 1 / 13 ( senary) the only difference would be u have to use more digits as far as i can see.

12. Nov 28, 2009

### HallsofIvy

There are, after all, organized groups supporting, say, base 12 and even some people plugging for base e!

As rasmhop said, there are exactly the same number of irrationals in any numeration system. The distinction between irrational and rational numbers is independent of the numeration system. As for "terminating" and "repeating" decimals, there really isn't that much difference in difficulty of working with them.

13. Nov 28, 2009

### Staff: Mentor

I vote for hexadecimal! It is so much easier to do a binary search in hexadecimal than decimal and it is more concise than binary or octal.

14. Nov 28, 2009

### DaveC426913

Nah. Doesn't support thirds. 12 is divisible by 2,3,4 and 6.

15. Nov 28, 2009

### hamster143

The way to go is to teach the general population to use hexadecimal, since it's already universal as an internal representation in computers, and to popularize the () notation:

1/2 = 0.8
1/3 = 0.(5)
1/4 = 0.4
1/5 = 0.(3)
1/6 = 0.2(A)
1/7 = 0.(249)
1/8 = 0.2
1/9 = 0.(1C7)

To improve usability, we can replace () with a second dot:

1/6 = 0.2.A
1/9 = 0..1C7

16. Nov 28, 2009

### Integral

Staff Emeritus
I am torn between base 12 and hexadecimal. Both have nice features, the number of prime divisors for 12 is handy, as is the correspondence with binary for base 16.

What ever 10 is the worst of the lot. With the biggest nastiness being the inability to precisely convert .1 (decimal) to binary.

Unfortunately there is no hope of ever changing, all this is just nerdy pipe dreams.

17. Nov 28, 2009

### Mensanator

I prefer Slot Machine Arithmetic. See http://mensanator.com/rotanasnem/cherries/cherries.htm" [Broken]

Last edited by a moderator: May 4, 2017
18. Nov 29, 2009

### pzona

I was reading about the advantages of the base 8 system a few weeks ago, and the book I was reading from mentioned something about some ancient Central American civilization using the base 8 system. The author asked mathematicians about why this might be advantageous, and they gave answers like "8 has more factors than 10," "8 is a power of 2," etc. However, when he asked a group of children, they said that this civilization was just counting the spaces between their fingers; I thought it was pretty interesting.

19. Nov 30, 2009

### hamster143

Interesting. There are also some languages that use base 12 because of the number of phalanges on four "main" fingers. And there's a couple of tribes in New Guinea that use 27, and no one knows for sure how that came about. But most cultures, from Chinese to Greeks to Maya, came up with different varieties of base 10 independently of each other.