Why would my cat urinate on the linoleum floor when she has a litter box?

she might have a kiddney problem and she's gettiing very old. she needs to see the vet and if there is nothing wrong with her idk what to tell u cuz more than likely there is something wrong with her. a friend of mine had a 15 year old cat named Ashley and he was having similar issuses and when my friend finally got ready to take him to the vet and she was getting her coat he died right then, he just fell over. I highly recommend seeing the vet, don't wait until it's too late.