# Maths joke!



## robert@fm (Oct 9, 2015)

I can think of three members (northerner, AlisonM and Redkite) who will get this one, there may of course be plenty of others.


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## Redkite (Oct 9, 2015)

very good!


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## silentsquirrel (Oct 9, 2015)

Not natural! But very good!   (from an ex Maths teacher, stress heavily on the EX)


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## robert@fm (Oct 9, 2015)

I love that "not natural" pun.


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## David H (Oct 9, 2015)

Pi = 2.1417 So not a rational number (2, 3, 4 etc)

eye dot = minus quantity so not real >0

I think.


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## silentsquirrel (Oct 9, 2015)

David H said:


> Pi = 2.1417 So not a rational number (2, 3, 4 etc)
> 
> eye dot = minus quantity so not real >0
> 
> I think.



Not quite, David!

Rational numbers are those that can be written exactly as a fraction, so does include whole numbers (eg 2 = 2/1) but also includes terminating decimals, (so 2.1417, which is only an approximation for pi, as is 22/7, IS rational, as 2.1417 = 21417/10000), and recurring decimals eg 0.66666....... = 2/3.

Pi is irrational as it is a non-terminating decimal with no pattern in the figures, so also not a recurring decimal. Others are eg root 2.

Real numbers do include negative numbers, but i is not real because it is an imaginary number - the square root of -1.


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## TheClockworkDodo (Oct 9, 2015)

Not a maths person, but my partner is, and some of it must have got through over the years because it made me laugh.  I will send it on to him.


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## Andy HB (Oct 11, 2015)

Mr pedant here,  but Pi is 3.141592654 to 9d.p. So is 3.1416 to 4 d.p.

Andy


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## trophywench (Oct 11, 2015)

Glad you said that Andy - I know 1961 was a long time ago - but I swear that's what we were told, too! - Three and a seventh, 3.14 !


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## robert@fm (Oct 11, 2015)

trophywench said:


> Glad you said that Andy - I know 1961 was a long time ago - but I swear that's what we were told, too! - Three and a seventh, 3.14 !



That's what I was taught (about ten years later) as well; 22/7, which is accurate to two fractional places (3.142857...). Hence International Pi Day, 22 July. Although 355/113 is a better rational approximation (3.1415929..., six fractional places).


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