The combined equation of the lines passing through the origin and having slopes $\frac{2}{3}$ and $-\frac{2}{3}$ is

In a meter bridge experiment,a resistance of $9 \Omega$ is connected in the left gap and an unknown resistance $x$ (where $x > 9 \Omega$) is connected in the right gap. If the resistances in the gaps are interchanged,the balancing point shifts by $10 \text{ cm}$. The value of the unknown resistance is: (in $\Omega$)

$A$ bag contains $6$ white and $4$ black balls. Two balls are drawn at random. The probability that they are of the same colour is:

The radius of gyration of a uniform thin rod of length $L$ about an axis passing normally through its centre of mass is:

When a certain metallic surface is illuminated with monochromatic light of wavelength $\lambda$,the stopping potential for photoelectric current is $3V_0$. When the same surface is illuminated with light of wavelength $2\lambda$,the stopping potential is $V_0$. The threshold wavelength of this surface for the photoelectric effect is:

Let $A$ and $B$ be independent events with $P(A)=0.3$ and $P(B)=0.4$. Find $P(A | B)$.