List of top General Aptitude Questions on Permutation and Combination asked in GATE CS

Two wizards try to create a spell using all the four elements, water, air, fire, and earth. For this, they decide to mix all these elements in all possible orders. They also decide to work independently. After trying all possible combinations of elements, they conclude that the spell does not work. How many attempts does each wizard make before coming to this conclusion, independently?
The least number of squares to be added in the figure to make AB a line of symmetry is: \begin{center} \includegraphics[width=6cm]{10.png} \end{center}