In the given circuit, the current flowing through the resistance $20\  \Omega$ is $0.3 \mathrm{~A}$, while the ammeter reads $0.9 \mathrm{~A}$. The value of $\mathrm{R}_1$ is_____________ $\Omega$.
  • A$12$
  • B$78$
  • C$45$
  • D$30$
JEE MAIN 2024, Diffcult
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