If S= {2, 3, 4, 5, 7, 9} , then the number of different three-digit number (with all distinct digits) less than 400 that can be formed from S is?
Correct Answer: 20
Explanation:
The hundred place will be reserved for 3 or 2
5 digits are free to fill rest two places i,e., of tens and unit. Number of required 3 digit number = 2 x 5C2 = 20
