Q.
In a Wheatstone bridge (see fig.), Resistances $P$ and $Q$ are approximately equal. When $R = 400 \; \Omega$, the bridge is equal. When $R = 400 \; \Omega$, the bridge is balanced. On inter-changing $P$ and $Q$, the value of $R$, for balance, is $405 \; \Omega$ .
The value of $X$ is close to :
Solution: