the galaxy 4 tablet says it's charging but isn't??

[AC Question]

I plugged my tablet in today and it will say it's charging but after a while I checked on it and it was charging very slowly. Well then it reached 64% but it wouldn't go up any further so I restarted it and suddenly the battery was only at 40%! Lately my tablet will say it is on 20% or higher and suddenly shut off and when I turn it back on it says 1%... Is my battery fried, I don't know what I could have possibly done for it to do this but, even now it says it is on forty but I'm positive it is probably not correct... Can anyone tell me if they've had this problem or if maybe I should buy a new tablet?