$a, b, c$ are real numbers. The quadratic equation $a x^2-b x+c=0$ has equal roots, which is $\beta$, then

The following figure shows the data of students enrolled in 5 years (2014 to 2018) for two schools P and Q. During this period, the ratio of the average number of the students enrolled in school P to the average of the difference of the number of students enrolled in schools $P$ and $Q$ is

A circle with center $O$ is shown in the figure. A rectangle $P Q R S$ of maximum possible area is inscribed in the circle. If the radius of the circle is $a$, then the area of shaded portion is $\_\_\_\_$ .

It is quarter past three in your watch. The angle between the hour hand and the minute hand is $\_\_\_\_$ .