How many three digit odd numbers can be formed by using the digits 1,2,3,4,5,6 if the repetition of digit is not allowed:
None of these
For a number to be odd, we must have 1,3 or 5 at the unit's place. So there are 3 ways for filling the unit's place.
Since the repetition of digits is not allowed, the ten's place can be filled with any of the remaining 5 digits in 5 ways. Now, four digits are left, so hundred's place can be filled in 4 ways.
So, required number of numbers = 3 x 5 x 4 = 60