the black keys on the piano are sharps and flats. If the note is flat they you will play the next key to the left. If they note is sharp, you will play the next key to the right.
They play sharps/flats. For example, the black key between the D key and E key plays D# / Eb
There are 36 black keys, 52 white keys; 88 keys in total. So the fraction in the number of black piano keys is 36/88. Simplify: 9/22.
36 on an piano..