11. How many 3-digit natural numbers are there where at least one of the digits is equal to 4?
(A) 252
(B) 196
(C) 180
(D) 225
(E) 216
Problem 11. The correct answer is $\mathbf{( A )}$.

The numbers from 100 to 999 (inclusive) without any digit being 4 are a total of $8 \cdot 9 \cdot 9=648$. Those where there is at least one 4 are therefore $900-648=252$.