Question

How many three-digit numerals can be formed from the digits 4,5,6,7 and 8 if no digit is repeated? ​

Answer 1

imagine this as an experiment:

There are three digits.

The first one may be any of the 4 possibilities (it does not matter that they are numbers).

Then, the second one may be any of the remaining 3 possibilities.

Then, the third one may be any of the remaining 2 possibilities.

We consider 567 and 576 to be different 3-digit numbers, so they are both counted.

This gives 4*3*2 = 24 possible 3-digit numbers. You can list them pretty easily:

FOR A= 5 TO 8

FOR B=5 TO 8

IF (B<>A) THEN

FOR C= 5 to 8

IF ((C<>A) AND (C<>B)) THEN OUTPUT (A,B,C)

NEXT C

NEXT B

NEXT A