geometry
posted by please help me out!!! please on .
In the English alphabet, there are 7 capital letters that look the same after being rotated 180∘. Those letters are H, I, N, O, S, X, and Z. How many different 3 letter "words" can be made from these letters such that when the word is rotated 180∘, the resulting word is the same?

Clearly the 1st and 3rd letter must be the same, but the middle can be any of the 7 letters
number of ways = 7 x 7 x 1 = 49