Question

How many four digit numbers can be formed from the digits 1, 3, 5, 7 and 9 if no digit may be repeated in a number

Answer 1

Numbers: 1,2,4,5,7,8
There are 4 digits __ __ __ __
1st digit can be filled by any of the 6 numbers
Similarly 2nd, 3rd and 4th
Hence each digit will have 6 possibilities
Therefore no.of 4 digit numbers that can be formed are 6 x 6 x 6 x 6 = 1296