Yesterday, we showed this diagram from the April-May 1970 issue of Science & Electronics magazine and asked what current is shown on the ammeter.

The puzzle is easier than it appears, once you see the trick.  The answer is 3 amps.  Despite the confusing diagram, the three resistors are wired in parallel, so the total resistance is 1 ohm.  You can do the math in your head using the “reciprocal of the reciprocals” method.  1/3 + 1/3 + 1/3 = 1, and 1/1 = 1.  To get the current, it’s 3 volts divided by 1 ohm, which equals 3 amps.