In a parallel combination, the voltage remains the same across each resistor but the current gets divided. Let I1, I2 and I3 be the current across resistors R1, R2 and R3, respectively.
I = I1 + I2 + I3
V = IR, V = I1R1, V = I2R2, V = I3R3
So, the total resistance is the sum of the reciprocal of the individual resistances.