im in year 7 so can someone help me with that modulo thing.. i nedd someone to explain it to me. :confused:

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- Aug 11th 2006, 01:58 AMxXxSANJIxXxwhat is mod??
im in year 7 so can someone help me with that modulo thing.. i nedd someone to explain it to me. :confused:

- Aug 11th 2006, 06:17 AMJameson
Here's a brief Wikipedia explanation.

http://en.wikipedia.org/wiki/Modular_arithmetic - Aug 11th 2006, 07:07 AMThePerfectHacker
Sometimes for basic explanations Wikipedia is not ideal for it is complicated.

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$\displaystyle a,b,n$ are integers and $\displaystyle n\not = 0$

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When we write,

$\displaystyle a\equiv b (\mbox{mod } n)$

We mean that $\displaystyle a-b$ is divisible by $\displaystyle n$.

For example,

$\displaystyle 5\equiv 3 (\mbox{mod } 2)$ because, $\displaystyle 5-3=2$ which is divisible by two.

For example,

$\displaystyle 5\not \equiv 2 (\mbox{mod } 2)$ because $\displaystyle 5-2=3$ which is not divisible by 2. - Aug 11th 2006, 07:19 AMSoltras
You can think of doing modular artithmetic kind of the same way you would, say, figure time on a clock.

In modulo 12, 10+3 = 1

because 10+3=13, of course, but 13 mod 12 = 1 because 13 divided by 12 leaves a remainder of 1.

Similarly, on a clock, 10pm + 3 hours = 1 am, not 13pm.

And then 1:00 + 18 hours = 1:00 + 6 hours = 7:00.

Because 18 mod 12 = 6.

So you've been using modular arithmetic as long as you've been telling time without knowing it was modular arithmetic. That knowledge will hopefully make you more comfortable with using it now in other modulos than 12. - Aug 11th 2006, 07:34 AMdan
Can’t (a mod b) be defined as the integer remainder of a/b ??....more or less :confused:

Dan - Aug 11th 2006, 07:47 AMThePerfectHackerQuote:

Originally Posted by**dan**

- Aug 11th 2006, 07:55 AMGlaysher
Year 7 means 11 years old if he is from England so would probably not be familiar with that notation. However it would not be part of the syllabus either so you never know.

If I'm right he need a different solution to his previous post - Aug 11th 2006, 08:22 AMdan
ph,

In your post about mod you used what looked like an equals sign but it had three lines. I have never seen that before ...what does it mean?

Dan - Aug 11th 2006, 08:27 AMQuickQuote:

Originally Posted by**dan**

- Aug 11th 2006, 08:31 AMRebesques
It's just notation, so long as you can just solve problems and not mind! :)

(Actually, $\displaystyle a\equiv b \ {\rm mod}n$ means a and b are members of the "equivalence relation" defined by: "having the same residue when divided by n"). - Aug 11th 2006, 09:20 AMdan
k thanks

dan