Question

How many $6$ digit number are there in all?

Answer 1

Estimate the total count of required natural numbers:

The smallest $6$ digit number is $100000$.

The largest $6$ digit number is $999999$.

Therefore, the total number of $4$-digit numbers

$=(999999-100000)+1$

$=899999+1$

$=900000$

Hence, there are $900000$ total $6$ digit numbers.