My Quick Fix

Problem
Parallel resistances can be are hard to understand because your dealing with a ratio not a sum. If you had two 10 ohm resistors connected in parallel, the total resistance accross the two would be 5ohms – this much is fairly easy to grasp because both resistors would share the current equally. But as soon as the values are different, each resistor handles a different share of the current.
Solution
To work out the total resistance accross 2 or more resistors connected in parallel you need this formula:
Rtotal = 1 / ( (1/R1) + (1/R2) …