Question

resistance increases if the resistors are connected in series and decreases if the resistors are connected in parallel

Answer 1

When resistors are connected in parallel, the supply current is equal to the sum of the currents through each resistor. In other words the currents in the branches of a parallel circuit add up to the supply current. When resistors are connected in parallel, they have the same potential difference across them.

Answer 2

It is because in series the pathway of current flow is one.so resistance increases.due to hinderance in the motion of current across the conductor.
while in parallel the current is divided into different paths so resistance offered by current is less as compared to in seris