In the given figure, AB is diameter and PC is tangent to the circle with center O. If AP = 40 cm, CP = 20 cm, find the radius of the circle.

Solve the quadratic equation x² - 3(x + 3) = 0 and give your answer correct to two significant figures.

Using remainder theorem, factorise 6x³ - 11x² - 3x + 2 completely.

The following table shows the distribution of the marks obtained by 50 students in an aptitude test.

Find the mean, the median and the mode of the distribution.