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.

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.

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.