The number of solutions of the system of equations $2x + y - z = 7$,$x - 3y + 2z = 1$,and $x + 4y - 3z = 5$ is

$A$ geostationary satellite is revolving around the earth. To make it escape from the gravitational field of the earth,its velocity must be increased by ........ $\%$

Two resistances $X$ and $Y$ are connected in the two gaps of a meter bridge,and the null point is obtained at $20 \text{ cm}$ from the zero end. When a resistance of $20 \text{ } \Omega$ is connected in series with the smaller of the two resistances $X$ and $Y$,the null point shifts to $40 \text{ cm}$ from the left end. The value of the smaller resistance in ohms is:

Heterosis is . . . . . . .

The sum of all the solution $(s)$ of the equation $\sin^{-1} 2x = \cos^{-1} x$ is

The following four wires of length $L$ and radius $r$ are made of the same material. Which of these will have the largest extension,when the same tension is applied?