A two-digit number exceeds the sum of the digits of that number by 18. If the digit at the unit's place is… · ABC26GN1730
Subject: General Aptitude · Chapter: Problems on Numbers
A two-digit number exceeds the sum of the digits of that number by 18. If the digit at the unit's place is double the digit in the ten's place, what is the number?
(a)24
(b)42
(c)48
(d)Data inadequate
Answer
Answer (as printed): A
Explanation
Let the ten's digit be $x$. Then, unit's digit $=2 x$. Number $=10 x+2 x=12 x$; Sum of digits $=x+2 x=3 x$. $$\therefore \quad 12 x-3 x=18 \Leftrightarrow 9 x=18 \Leftrightarrow x=2 .$$ Hence, required number $=12 x=24$.
Explanation as extracted from the printed page; notation may be imperfect.