How many numbers are there between 100 and 1000 in which all digits are distinct.	Select the correct option:
A) 900
B) 648
C) 720
D) 252
E) 729
We know that numbers between 100 and 1000 will be 3 digit integers.   Let the arrangement be ABC where A,B,C represent distinct digits.   We have 9 options for A (as 0 can not start a 3 digit number), 9 options again for B and 8 for C, giving a total of  9*9*8= 
<gadget id="calculator"> 9*9*8</gadget>
<output>648</output>
648 options.   ANSWER 648
<result>B</result>
How many numbers are there between 100 and 1000 in which all digits are distinct.