1aHow many strings of length 10 can be formed using the firs

1.(a).How many strings of length 10 can be formed using the first 10 letters of the alphabet, each one exactly once?

(b)What if we also require that the string starts with “E” or ends with “BA”?

a). First ten alphabet are A,B,C,D,E,F,G,H,I,J

Now we have to find the no. of string of length formed from using this alphabet but each alphabet used at once only

We have make a word of 10 alphabet, i.e. for first letter we have 10 choice

for second 9 choice

Similarly, the no. of way is 10*9*8*7*6*5*4*3*2*1 = 10!

= 3628800

b). There is restriction that word should be start with E and end with BA, than seven alphabet are left

E _ _ _ _ _ _ _ B A ,here we have 7 choice to make a letter

E 7 6 5 4 3 2 1 B A

7! = 5040 way