Question

The minimum number of digits required to form every number which is greater than 900 and less than 9,000 is:

Answer 1

For unit place numbers can range from 0-9 that is total 10 digits

For tens(10th) place number can range from 0-9 that is again 10 digits (0,1,2,3,4,5,6,7,8,9)

Similarly for hundred(100th) place again 10 digits.

But for 1000th place it can only range from 1-9 that is total 9.

We cannot include 0 here as the number will then start from 0 means ex-0459 which only means 459.

So the minimum no of digits required are : 10+10+10+9 =39  

39 is the correct answer.