 :::I cannot tell that they are four separate methods. It's possible that there is a hidden assumption which underlies all four calculations which throws them all off the same way. Personally, under the circumstances my reaction would be to assume that my calculations were wrong and try to find where the fault lies before assuming on my own that I'd done it right. Failing that, I would submit my calculations to someone else for verification. That's where we have a WP:RS issue with this guy: we don't have outside confirmation that his calculations make sense. And I imagine that most people competent to do so are not inclined to spend time doing so.   