Subject: General Aptitude · Chapter: Problems on Numbers · Exam: 2003 · Marks: · Difficulty:
A number consists of two digits. If the digits interchange places and the new number is added to the original number, then the resulting number will be divisible by
(a)3
(b)5
(c)9
(d)11
Answer
Answer (as printed): D
Explanation
Let the ten's digit be $x$ and unit's digit be $y$. Then, number $=10 x+y$. Number obtained by interchanging the digits $=10 y+x$. $$\begin{aligned} \therefore \quad & (10 x+y)+(10 y+x) \\ & =11(x+y), \text { which is divisible by } 11 . \end{aligned}$$
Explanation as extracted from the printed page; notation may be imperfect.