Factorial

[muskan]

Factorial is given by moving left side of a number till 1. 
4! =4*3*2*1
3!=3*2*1
2!=2*1
1!=1
But one is on right side of 0. How can we say that
0!=1
It must be 0. Please clear it.
  

[John Cuthber]

If I have three objects, for example a red ball, a blue ball and a green ball, there are 3! ways I can arrange them.

RGB

RBG

BRG

BGR

GBR

GRB

 

With just two objects there are 2! ways

RG

GR

And with 1 object there's only 1! way to arrange it

G

There's only 1 way to arrange zero objects

 

And that's why 0! =1

 

It's adopted as a convention so the maths gives sensible answers for things like probability.

 

Edited July 28, 2018 by John Cuthber