To find the resistance of a galvanometer by the half deflection method the following circuit is used with resistances $R_1 = 9970\,\Omega,$ $R_2 = 30\,\Omega$ and $R_3 = 0\,\Omega.$ The deflection in the galvanometer is $d$. With $R_3 = 107\,\Omega$ the deflection changed to $\frac {d}{2}$The galvanometer resistance is approximately ............... $\Omega$
JEE MAIN 2013, Diffcult
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