The reciprocal of the combined resistance R of two resistances Ry and R 2 connected in parallel is equal to the sum of the reciprocals of the individual resistances . If the two resistances are connected in series their combined resistance is the sum of their individual resistances . If two resistances connected in parallel have a combined resistance of 20 0 1 and the same two resistances have a combined resistance of 81 2 when connected in series , what are the resistances ? ( Show all your work . ) 1 + R2 RT R 1 RT RX + R 2