For the series combination of resistors, the combined resistance is the sum of all the resistances. So, if there are N resistors in series, the combined resistance is

R= R1 + R2 +...+ Rn

In a series circuit, the R value will always be greater than the largest of the individual resistances.

For the parallel combination of resistors, the reciprocal of combined resistance is the reciprocal of the individual resistor added together to get the sum. If there is N resistors in parallel, the combined resistance is

1/R= 1/R1 + 1/R2 +...+ 1/Rn

When resistors are connected in parallel, the combined resistance R is smaller than the smallest individual resistance, because the reciprocal of the combined resistance, 1/R is equal to the sum of the individual resistances. When more resistors are added to parallel, there will be more paths for main current to flow through. In order to maintain the same potential difference across the parallel section, a larger current is used. Using V=IR with the same potential difference and increased current, a lower R for the parallel section would result.

R= R1 + R2 +...+ Rn

In a series circuit, the R value will always be greater than the largest of the individual resistances.

For the parallel combination of resistors, the reciprocal of combined resistance is the reciprocal of the individual resistor added together to get the sum. If there is N resistors in parallel, the combined resistance is

1/R= 1/R1 + 1/R2 +...+ 1/Rn

When resistors are connected in parallel, the combined resistance R is smaller than the smallest individual resistance, because the reciprocal of the combined resistance, 1/R is equal to the sum of the individual resistances. When more resistors are added to parallel, there will be more paths for main current to flow through. In order to maintain the same potential difference across the parallel section, a larger current is used. Using V=IR with the same potential difference and increased current, a lower R for the parallel section would result.