2017
Problem - 3719
Let $S(n)$ equal the sum of the digits of positive integer $n$. For example, $S(1507) = 13$. For a particular positive integer $n$, $S(n) = 1274$. Which of the following could be the value of $S(n+1)$?
Answer
D
By the MOD $9$ technique, we have $n\equiv S(n) \equiv 1274\equiv 5\pmod{9}$. Therefore $ n+1 \equiv 6\pmod{9}$. Among the given choices, only $1239$ satisfies this constraint.