Question

If ∑ = {a, b, c, d, e, f} then number of strings in ∑ of length 4 such that no symbol is used more than once in a string is

(a) 35

(b) 360

(c) 49

(d) 720

The question was asked in my homework.

This question is from Finite Automata and Regular Expressions topic in division Compiler Introduction of Compiler

Answer 1

Right answer is (b) 360

Best explanation: Here string length is 4 so we create string of length 4 by 6 values firstly we arrange any value by 6 methods. Then Remaining numbers are 5 so we can arrange them by 5 methods then remaining numbers are 4 so we arrange them by 4 methods and then 3.Thus 6*5*4*3=360.