Question

Three resistors of 6-ohm resistance are connected in delta. Inside the delta, another 6-ohm resistor  is connected in wye. Find the resistance between any two corners. 

Answer 1

$R_1=R+R=2R\Omega\\R_2=R+R=2R\Omega$

$R_1,R_2,R'$ Is parallel combination

$\frac{1}{R_{net}}=\frac{1}{R_1}+\frac{1}{R_2}+\frac{1}{R'}$

$\frac{1}{R_{net}}=\frac{1}{2R}+\frac{1}{2R}+\frac{1}{R}$

$\frac{1}{R_{net}}=\frac{4}{2R}\\R_{net}=\frac{R}{2}$