Our girls are learning how to add multiple numbers at once. Recently they started stacking five or six numbers in a row and adding them. You know what? I check their math homework with a calculator. As I like to tell them, I've already been through second grade. I know how to do the math. I just don't want to.
Plus, if I'm really honest, I'd say that once I did the math in my head and came up with the wrong answer. Given that I still haven't lived down that error, I'm not interested in making another math mistake.