Mental Floss

Brain Game: Let's Get Digital


Today's Brain Game is rather taxing; it's a puzzle I've had in my head for some time and finally brought out to see the light of day. It has to do with old-fashioned LCD/LED digit indicators. You know the type, with seven bars that combine to make all the digits from zero to nine:

segments1.gif /

As an example, here's what the numbers zero to nine would have looked like on my broken clock, with the middle segment is missing:

segments2.gif /

As you can see in the diagram, even if you KNOW the middle bar is bad, you can't tell a zero from an eight because you would never know if that segment was supposed to be blank (meaning it's a zero) or supposed to be filled (meaning it's an eight).

Recently, I plugged in all the possible numbers and segments and found the answer. There are TWO segments of the seven which, if you KNOW they are the ones that fail to display, will still allow a smart viewer to tell the time. In fact, even if BOTH these segments disappear, you can still tell the time as long as you know the specific two that have failed.

The Brain Game? Figure out which two. Good luck!

HERE'S the answer.


The two segments that CAN go blank without affecting one's ability to distinguish the numbers are the bottom horizontal segment and the lower-right vertical segment. See the graphic below for details:

segmentsf2.gif /