Question

How many numbers are there between 100and 1000 such that every digit is 2 or 9?

Answer 1

The numbers between 100 and 1000 are clearly the three digit number.
All the three digits can be filled by 2 ways.
=> 2*2*2 = 8 ways

Answer 2

27+27 there are 54 digit in between 100 and 1000 such that every digit is 2 or 9