How many three digit numbers are there in all?
(a) 100
(b) 101
(c) 99
(d) None of these
As we know, there are 10 digits i.e.,0,1,2,3,4,5,6,7,8,9.
We can not use '0' at the hundred's place.
So, we can use only 9 digits at the hundred's place.
Also, we can use 10 digits at the remaining two places.
So, total numbers of 3-digit numbers=9×10×10=900
The total number of 3 digit numbers =900
Hence, the correct answer is option (D).