Whats 25*253? Its a hard sum to do (the answer is 6325). Calculator is usually the only way to work out such a sum with out being a maths genius. But spotlight has a cool little feature than enables you to do basic calculations.
The idea behind this tip is that you insert you sum into the spotlight box in the menu bar your computer whirs away and the result is outputted at the top of the list along with any applicable results.
Its a very cool little trick and is great for those quick sums. It quickly bring up spotlight press command + space.