I really can't understand uncertainty

[Shing]

I really can't understand "uncertainty"

Hi guys,
I really can't understand "uncertainty"...
How it works, and Why it works
I don't understand..
Like why:
4+/-0.5 x 5.2+/- 0.2
=4x5.2 +/- 0.5 x 0.2?

Would anyone be kind enough to elaborate a bit for me?
Thanks for reading

 

[Shing]

Hi guys,
I really can't understand "uncertainty"...
How it works, and Why it works
I don't understand..
Like why:
4+/-0.5 x 5.2+/- 0.2
=4x5.2 +/- 0.5 x 0.2?

Would anyone be kind enough to elaborate a bit for me?
Thanks for reading

Why moved it here?
It is not homework, not coursework either That was just an example...
If any naive post will be moved, then who will ask questions here?