Why do you round pi

oh and just incase you were wanting to know why you round pi it's because its an infinite number, so you wouldn't be able to solve anything! you'd be dead before you finished a problem

The difference between an expression and an equation is that an expression doesn't have an equal sign, and an equation does.

(That is the basics)

an expression does not have an = sign. and equation does. for an expression, you just have to simplify it until you cant anymore

Yes saseflower is right.

the digits for pi go one forever  (It is an irrational number)

So you can either leave it as the symbol pi

or you have to round it off.