Answer:
The answer is 1920, right? Here is how-
The numbers must contain at least three digit and can go above that which means the answer has 3 4 5 and 6 digits all together.
For three digits , there will be 6*5*4 = 120
For 4 Digits, There will be 6*5*4*3=360 possible numbers
For 5 digits , there will be 6*5*4*3*2 = 6! = 720
For 6 digits, there will be 6*5*4*3*2*1 = 6! = 720
<Note- the digits are non repeating as the question said it to be “different digits” >
Now add them up = 120+360+2*720 = 1920
Explanation: