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## Modulus of Negative Numbers

The Quickest and easiest way to find the mod of a negative number is by using the below property

`if a = (b) mod c then a = (c*k + b) mod c (where k = 1,2,3.......) `

It simply says that the value of a is unchanged when we add a multiple of c to b

Example

```
a = (10) mod 3 we all know that a = 1 Now
a = (3*1 + 10) mod 3 - a is still = 1
a = (3*2 + 10) mod 3 - a is still = 1
a = (3*3 + 10) mod 3 - a is still = 1
a = (3*4 + 10) mod 3 - a is still = 1
```

So adding any multiple of 3 (> 0) to 10 does not effect the value of a

Now we use this to our advantage in finding mod of negative numbers

Example

a = (-10) mod 3

Now i add 12 to 10 as 12 is a multiple of 3 and hence the value of a will remain unchanged

so a = (3*4 – 10) mod 3 = 2 mod 3 = 2

easy isnt it?

Another example

a = (-340) mod 60

So a = (60*6 – 340) mod 60 = (360-340) mod 60 = 20 mod 60 = 20

Categories: Technology

Awesome Stuff Dude!! š Helped me a lot in ECC

i have lost touch with my math lately – glad it helped š

Thnx dude š

thank u

That was quick and direct too, it really helped me

was looking for this 20 mins couldnt understand whats going on came here and boom , thanks

thanks a lot..

thank u

Thank you , It is helpful,

Very helpful. Thank you

But why this is done this way is still a mystery. What’s the mathematica resoning behind this?

Can anyone help please???

Very useful.. thank you