Question

Hhow many no. Are there between 100 and 1000 so that every digit of the no. Is either 2 or 7 ?

Answer 1

Answer:

the no.from 100 to 1000 are all 3 digit no. except 1000 nd as we know it can be neglected

so for unit place we have 2 choice either 2 or 7 same for tense place nd hundred place so the answer is 2×2=4