Subject: General Aptitude · Chapter: Problems on Numbers · Exam: · Marks: · Difficulty:
A two-digit number becomes five-sixth of itself when its digits are reversed. The two digits differ by one. The number is
(a)45
(b)54
(c)56
(d)65
Answer
Answer (as printed): B
Explanation
Since the number reduces on reversing the digits, so ten's digit is greater than the unit's digit. Let the unit's digit be $x$. Then, ten's digit $=(x+1)$. $$\begin{aligned} \therefore \quad 10 x+(x+1) & =\frac{5}{6}[10(x+1)+x] \Leftrightarrow 66 x+6 \\ & =55 x+50 \Leftrightarrow 11 x=44 \Leftrightarrow x=4 . \end{aligned}$$ Hence, required number = 54.
Explanation as extracted from the printed page; notation may be imperfect.