Five resistors each of value m are connected between points A and F as shown in figure if two similar wires are connected one between points B and D and the other between C and E .the effective resistance between points A and F will be

When resistors are connected as mentioned, BDEC would form a wheatstone bridge and so CD branch can be neglected. Then resistance of branch BDE and BCE, both becomes 2m. Hence resistance across B and E becomes m. Hence total resistance across A and F becomes 3m.