Two resistance of $100\ \Omega$ and $200\ \Omega$ are connected in series with a battery of $4 \mathrm{~V}$ and negligible internal resistance. $A$ voltmeter is used to measure voltage across $100 \Omega$ resistance, which gives reading as $1 \mathrm{~V}$. The resistance of voltmeter must be ___$\Omega$.
JEE MAIN 2024, Diffcult
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