A wire of radius $r$ has resistance $R$. If it is stretched to a radius of $\frac{{3r}}{4}$, its resistance becomes
  • A$\frac{{9R}}{{16}}$
  • B$\frac{{16R}}{9}$
  • C$\frac{{81R}}{{256}}$
  • D$\frac{{256R}}{{81}}$
Medium
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