In the ASCII character set, the binary representation for the character 'Z' (which is 90 in decimal) is 01011010
. To find the binary representation for the number 91, you simply add 1 to the binary representation of 90.
Starting from 90:
01011010 (90 in binary)
Adding 1:
01011010
+ 1
-----------
01011011 (This is 91 in binary)
Therefore, the binary number that represents the number 91 is 01011011
.