The sum of the digits of a two-digit number is 1/5 of the difference between the number and the number… · ABC26GN1740
Subject: General Aptitude · Chapter: Problems on Numbers
The sum of the digits of a two-digit number is $\frac{1}{5}$ of the difference between the number and the number obtained by interchanging the positions of the digits. What is definitely the difference between the digits of that number?
(a)5
(b)7
(c)9
(d)Data inadequate
(e)None of these
Answer
Answer (as printed): D
Explanation
Let the ten's digit be $x$ and unit's digit be $y$. Then, $x+y=\frac{1}{5}[(10x+y)-(10y+x)] \Leftrightarrow 5x+5y=9x-9y \Leftrightarrow 4x=14y$. Thus, the value of $(x-y)$ cannot be determined from the given data.
Explanation as extracted from the printed page; notation may be imperfect.