Number of 3 digit numbers with atleast one 7
= (10*10) + (10*9) + (10*9) - 10 - 10 - 9 + 1
= 100 + 90 + 90 - 10 - 10 - 9 + 1
= 252
Number of 3 digit numbers with no 7 in any of its digits
= 900 - 252
= 648
Probability(Number not having digit 7)
= 648 / 900
= 18 / 25.
Option D) is the answer ...