I was just bouncing around LinkedIn (as you do) when I ran across a puzzle someone had posted with a simple caption of “Interview Question.”

This is one of those tricky little rascals that you either get right or wrong. Well, I guess that’s true of all problems of this nature. That’s not really what I meant.

A bit of a poser (Click image to see a larger version)

What I was trying to say is that this is one of those problems whose presentation can easily lead you into looking at it from the wrong point of view, which subsequently guides you to an incorrect solution.

My knee-jerk reaction was that this puzzle wasn’t too difficult. Almost immediately, I saw that my friend Steve Leibson had posted the correct answer, which (to be honest) was no great surprise.

As an aside, did you see the column Steve posted today: A Brief History of PCBs: Where Did Printed Circuit Boards Come From? As is always the case with Steve’s writings, I learned all sorts of things I never knew before, but we digress…

Just for giggles and grins, I shared this little conundrum with a few friends by email, only to be surprised by the selection of incorrect answers I received in response.

Looking at these responses, it was obvious where each of my friends had gone wrong. It was also obvious that each had simply glanced at the circuit and then made an on-the-spot assumption upon which they had based their subsequent calculations.

What say you? Dare you resist?