Please enjoy the Think Thursday challenge from the mental_floss Brain Game. Good luck!

When writing out all the numbers from
ONE to ONE-HUNDRED (in English, of course)
which letter of the alphabet is only used TWICE?

Here is the SOLUTION.


The letter L.

It only appears in the numbers ELEVEN and TWELVE.

NOTE: The letter D also works here, as our clever readers pointed out, since it's used twice in ONE HUNDRED.