Find the equivalent resistances of the networks shown in the figure. between the points a and b.
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$\text{R}_\text{eff}=\frac{\Big(\frac{2\text{r}}{3}+\text{r}\Big)\text{r}}{\Big(\frac{2\text{r}}{3}+\text{r}+\text{r}\Big)}=\frac{5\text{r}}{8}$ 
$\text{R}_\text{eff}=\frac{\text{r}}{3}+\text{r}=\frac{4\text{r}}{3}$ 
$\text{R}_\text{eff}=\frac{2\text{r}}{2}=\text{r}$ 
$\text{R}_\text{eff}=\frac{\text{r}}{4}$ 
$\text{R}_\text{eff}=\text{r}$
$\text{R}_\text{eff}=\frac{\text{r}}{3}+\text{r}=\frac{4\text{r}}{3}$ $\text{R}_\text{eff}=\frac{2\text{r}}{2}=\text{r}$ $\text{R}_\text{eff}=\frac{\text{r}}{4}$ $\text{R}_\text{eff}=\text{r}$
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