Find the smallest positive integer n such that 11n - 1 is divisible by 105.
Select the correct option
A) 3  B) 4  C) 5  D) 6  E) 7

Rationale: the last digit of 11 n − 1 is 0 , so 5 always divides 11 n − 1 . also , checking the remainders when the powers of 11 are divided by 3 and 7 we get that 3 divides 11 n − 1 exactly when n is even , and 7 divides 11 n − 1 exactly when 3 divides n . correct answer d
Answer: D