The standard deviation of the numbers $22, 26, 28, 20, 24, 30$ is

$A$ tank with vertical walls is mounted so that its base is at a height $H$ above the horizontal ground. The tank is filled with water to a depth $h$. $A$ hole is punched in the side wall of the tank at a depth $x$ below the water surface. To have maximum range of the emerging stream, the value of $x$ is

The polar equation $\cos \theta + 7 \sin \theta = \frac{1}{r}$ represents a

Which of the following sets of atomic numbers corresponds to elements of group $16$?

Four resistors $A, B, C$ and $D$ form a Wheatstone bridge. The bridge is balanced when $C = 100 \ \Omega$. If $A$ and $B$ are interchanged,the bridge balances for $C = 121 \ \Omega$. The value of $D$ is (in $\Omega$)

Which of the following is a copper-releasing $IUD$?