Question

How many numbers of of three digits less than 500 can be found from integers 1, 2, 3, 4, 5, 6.
(Nothing is mentioned on question whether repetition is allowed or not)​

Answer 1

Answer:

4 possible 1st digit : 1, 2, 3, 4 (1st digits greater than 4 will be over 500)

6 possible 2nd digit : any of 1, 2, 3, 4, 5, 6, 7, except the digit we just used.

5 possible 3rd digit : any of 1, 2, 3, 4, 5, 6, 7, except the 2 digits we just used

Finally, we can form4×6×5=1204×6×5=120numbers