Question

Find the number of 4 digits tht can be formed using 1,2,3,4,5 if no repitition

Answer 1

Any number can come in the first position. So there are 5 chances. Second position can have any 4 numbers except the number chosen for the first position. Similarly 3rd position can have 3, 2nd 2 and last position only one number

So toal is 5x4x3x2x1=120