the letters of the word TUESDAY are arranged in a line,each arrangement ending with letter S. how many different arrangements are possible? How many of them start with letter D?

wtf


 

Tuesday has 7 digits. The 7 th place is occupied by S. Therefore remaining 6 digits can be arranged.
Therefore, 6 P6= 6! /6-6!
                         =6!=6*5*4*3*2*1
                         =720
if the word starts with D then remaining 5 digits have to be arranged.
therefore,5 P5=5! /5-5!
                      =5!=5*4*3*2*1=120