Find the resistance across

A and D

In order to find the total resistance, first we need to memorize the rule which we have learned which is , THE POINTS WHO’S ACROSS WE HAVE TO EVALUATE THE TOTAL RESISTANCE ARE THE GIVEN POINTS AND WE CONSIDER OR IMAGINE THAT A BATTERY IS CONNECTED TO THE CIRCUIT THROUGH THESE TWO POINTS ONLY .

And the rest are the normal points of the circuit.

A and D are the given points in this part of the question and the rest of the points are the simple points (that is B and C).

As the resistors in the line BC are in series and the resistors in the line AD are also in series with each other , so they will get added like integers or they will be simply added.

Now merge the points B into A and C into D , because they have same potential , all the three resistors are parallel to each other ,

By solving we will get ,

These two resistors are in parallel combination , so when we solve these two we will get ,

This is the resultant resistance.