How many symbols are there on a standard drum kit?

It depends on what kind of "standard" kit you're talking about. Every drum company has their own idea of a 'standard' drum kit. So, I'm just going to assume you are talking about a basic beginners drum kit. So, to get to your question, a beginners drum kit usually has a hi-hat, which is two cymbals put together, one on top of the other. The standard hi-hat size is about 13 to 14 inches. Next, there is the Ride. The standard size for a ride is about 20 inches, however, I've seen rides range anywhere form 18 inches to 26 inches. And finally, there is the Crash. Standard Crash sizes are usually about 16 inches, however, I have seen crashes range anywhere form 14 inches to 20 inches. So, to answer your question in short, there are usually 4 cymbals in a beginner's drum kit (if you are counting the hi-hat as 2)

Hope that helps!