Three resistors `1 Omega`, `2 Omega` and `3 Omega` are combined in series. What is the total resistance of the combination?

Three resistors 1Omega , 2Omega and 3Omega are combined in series. What Is the total resistance of the combination?

Three resistors 2 Omega , 4 Omega and 5 Omega are combined in parallel. What is the total resistance of the combination?

Three resistors 2Omega , 4Omega and 5Omega are combined in parallel. What is the total resistance of the combination?

How can three resistors of resistance 2 Omega 3 Omega and 6 Omega be connected to give a total resistance of (a) 4 Omega (b) 1 Omega ?