In Search of the Bogus Coins

The Puzzler

RAY: Here's how we're going to do it. We're going to take one coin from the first stack, and two coins from the second stack.

TOM: Then four, then eight.

RAY: There you go.

TOM: Sixteen, thirty-two, and sixty-four coins from the last stack.

RAY: Right. So no matter what weight you wind up, it's unique.
For example, if the pile you're weighing is seven grams over, the only way that could happen is if pile one, pile two, and pile three were overweight. If the pile were 63 grams over, that would mean all the stacks were bogus, except the last one.

Brilliant, eh?

TOM: Very, very good.

RAY: So who's our winner?

TOM: The winner is Tabetha Garrison from Harrisonburg, Virginia. And for having her answer selected at random from both of the right answers that we got, Tabetha's going to get a 26-dollar gift certificate to the Shameless Commerce Division of And with that certificate, Tabetha, you can knock off your Fathers' Day shopping and pick up a Car Talk necktie. It looks like a normal striped silk tie, but when you get up close if you can read between Dad's mustard stains you'll actually see that the stripes are made up of the names in small print, names from the Car Talk's euphonious list of credits.

[ Car Talk Puzzler ]

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