Question

A student ID number is a letter of the alphabet followed by 2 digits. How many different IDs are possible if the digits can be repeated?

Answer 1

Digits range from  0 to 9  That makes  10 double digits

number of permutation of 2 digits when they are different = 10*9 = 90

this gives 90 + 10  = 100 different ways to arrange the digits

combine this with e 26 letters in alphabet we get  number different IDs

 = 26*100 = 2600