Men have invented many things  without which our life may not have been as it is today.Electricity has been so far one of man's best inventions. Today, without electricity our life is unimaginable. Everything, almost everything, is dependent on electricity, be it trains, your breakfast and even its only because electricity was invented, you are able to get answer to this question. Based on electricity thousands  of inventions have been made so far.So undoubtably electricity has been one of the best inventions of man ever.
With help of computer and by using it we can do various things without which we all would be lost. So in my opinion computer is mans best invention. As far as working of computer is concerned it need power so electricity is also important. But computer is man's best invention. Because best invention never cause harm to anyone. But owing to power some accidents occurs which would harm many.
Mathematical Formulas because they are used in our daily usually and are very important.