Question

there are three source of resistance in parallel circuit. Two of them are rated at 20 ohms, the other at 10 ohms. What is the circuits total resistance

Answer 1

In paraller connection you can calculate the equivlant resistqnce from the relation :
1/R(equi) = 1/R1 + 1/R2 + 1/R3
1/R(equi) = 1/20 +1/20 + 1/10
1/R(equi) = 0.05+0.05+0.1 = 0.2
so, R(equi) = 5 ohms