Which of the following groups of transition metals are known as coinage metals?

The equation $\frac{1}{r} = \frac{1}{8} + \frac{3}{8} \cos \theta$ represents

Seven white balls and three black balls are randomly arranged in a row. The probability that no two black balls are placed adjacently is

$A$ circular disc of radius $R$ is removed from a bigger circular disc of radius $2R$ such that the circumferences of the discs touch. The centre of mass of the new disc is at a distance $\alpha R$ from the centre of the bigger disc. The value of $\alpha$ is

Sulphur trioxide is dissolved in heavy water to form a compound $X$. The hybridisation state of sulphur in $X$ is :

If the number of diagonals of a regular polygon is $35$,then the number of sides of the polygon is