Question

2. How many numbers are there between 100 and 1000 such that
(i) every digit is either 2 or 5
(ii) digit at unit's place is 5
(iii) atleast one digit is 5
(iv) exactly one digit is 5​

Answer 1

Answer:

Each one of the unit's ten's and hundred's places can be filled in 2 ways. Hence, the required number of numbers =(2×2×2)=8.