Mental Floss

Brain Game: Lighten Up


Here's a Tuesday Test Time to occupy a bit of your time. Enjoy!

We're all familiar with the the standard LCD/LED number displays as the one seen above (with seven segments that can be turned on and off to make up each digit). They've been used for years on watches, clocks, radios, and other devices that require numerical outputs. The example shown lights up 6 of the 7 available segments to display the number 9.

Suppose you had a one-digit display, like the one above, that counted from 0 to 9, then started over again and again. Now, suppose each segment of the display had a set limit of 10,000 light-up showings, and that any segment reaching that limit would immediately fail to light up. With this information in mind...

Which of the seven segments in the display would be the LAST to still remain working while the six others had already burned out?

Here is the ANSWER.


The last segment to remain would be the one in the lower left.

The lower-left segment only lights up 4 times when displaying the digits 0 through 9 (for the numbers 0, 2, 6, and 8).

All other segments light up at least 6 times when displaying the digits 0 through 9, so all of them would burn out first.