A difficult calculation

Set theory, Algebra, Modern Algebra, Geometry, Analytical Geometry, Trigonometry, Differential Calculus, Integral Calculus, Differential equation, Partial differential equation, Numerical Methods, Complex Numbers, Operation Research, Graph Theory, Statistics. Those were some of the difficult mathematical subjects that i studied during my college and in school. They involved a little amount of calculation and were quite easy. The most difficult calculation i encountered after entering the company was calculation and declaration of income tax. Was forced to spend two full days on this, since could not make head or tail about the process and rules. Later with the help of some senior colleagues in company was able to decipher but still i am not sure about the entire process. It was funny to find even seniors sharing the same opinion. So the tamil proverb "Aetu surakai kariku uthavathu"(book knowledge does not help much in life) seems to be true.