List of top General Aptitude Questions on Ratio and Proportion asked in GATE EE, GATE MA

The figure below shows the front and rear view of a disc, which is shaded with identical patterns. The disc is flipped once with respect to any one of the fixed axes 1-1, 2-2, or 3-3 chosen uniformly at random.
What is the probability that the disc DOES NOT retain the same front and rear views after the flipping operation?
The ratio of boys to girls in a class is 7 to 3. Among the options below, an acceptable value for the total number of students in the class is: