what is a button cell ?
A button cell is a small single cell battery in shape of a cylinder like a button. This cell is used to power small devises like, wrist watch, pocket calculator etc.
Ram put some buttons on the table. There were 4 blue, 7 red, 3 black and 6 white buttons in all. All of a sudden, a cat jumped on the table and knocked out one button on the floor. What is the probability that the button on the floor is blue?