You are Here: Home >< Maths

Announcements
1. Hello there,
I know the explanation is simple, but I've been having a mental block !

Suppose we are working with Z/5Z (where Z is the set of integers).

Why is it that [1] / [2] gives [3] ??? And why does [2] / [2] give [4] ????

I cant remember how you work these out?

Any help would be much appreciated.
2. Finding [1] / [2] is the same as solving 2x = 1 (mod 5).
Finding [2] / [2] is the same as solving 2x = 2 (mod 5).

It is easy to check which of the five possible values of x (0, 1, 2, 3, 4) is a solution.

For more complicated problems, Euclid's algorithm will solve the mod equations.
3. ok cool, that makes sense :

But then, why does [2]/[2] give [4] ??

If this [2]/[2] is equivalent to solving 2x = 2mod5, then 5 must be a factor of 2x - 2. But if x = 4, then 5 is a factor of 6, which is not true

cheers Jonny
4. It doesn't give [4], it gives [1].
5. thanks Mike,

yeah that's what I thought!!

There's an example in my notes which is wrong (or I must have copied down wrong haha).

Cheers mate!!

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 13, 2006
Today on TSR

### Four simple steps to get an A*

Here's all you have to do

### University open days

• University of East Anglia
All Departments Open 13:00-17:00. Find out more about our diverse range of subject areas and career progression in the Arts & Humanities, Social Sciences, Medicine & Health Sciences, and the Sciences. Postgraduate
Wed, 30 Jan '19
• Aston University
Wed, 30 Jan '19
• Solent University
Sat, 2 Feb '19
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams