4gb VS 8gb Ram

Hi ,
I want to buy laptop for college use ( internet browsing , writing on word , powerpoint , youtubes ... )
I found one is good for me but it come with 2 configurations first one ram 4gb for 450$ second one is ram 8gb for 550$
Do I really need to pay 100 $ more for extra 4 gb rams ? according to my use /.?

What OS are you going to run? Most (all that I've seen) new PC's come with Windows 10. 4GB will work but 8 is better. If you can afford the extra, go for it. What I tell my clients when they ask about purchasing a new PC is "buy overkill" (more than you think you need) or "as much as your wallet can stand".

I will use windows 8.1 pro

There is wisdom in what fireberd said. Most users will do very well with 4GB of RAM, especially given the uses you stated for your laptop. However, your needs may change in the future which is why it's best to buy as much computer as you can afford. It's cheap insurance compared to needing to buy a newer, more powerful computer a year or 2 down the road.

Thank you