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We expect knowledge to be intuitive and reasonable. And when it comes to parallel circuits, students' expectations are often challenged due to the following counterintuitive claim: the addition of more resistors in a parallel circuit leads to a decrease in overall resistance. In other words: add more resistors and get less resistance. The explanation for this counterintuitive claim is best explained by an analogy of parallel circuits to an automobile toll way. On a toll way, it is the toll booths that offer resistance to the flow of cars. To increase the rate of car flow, the toll way authority often decides to add another toll booth. The addition of this toll booth in a separate pathway would cause the overall resistance to lessen and the rate of car flow to increase. Adding more toll booths (resistors) in separate branches results in less overall resistance. Now that makes sense!
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