Subject: General Aptitude · Chapter: Problems on Numbers · Exam: 2003 · Marks: · Difficulty:
A certain number of two digits is three times the sum of its digits and if 45 be added to it, the digits are reversed. The number is
(a)23
(b)27
(c)32
(d)72
Answer
Answer (as printed): B
Explanation
Let the ten's digit be x and unit's digit be y. Then, 10x + y = 3 (x + y) ⇒ 7x – 2y = 0 ...(i) 10x + y + 45 = 10y + x ⇒ y – x = 5 ...(ii) Solving (i) and (ii), we get : x = 2 and y = 7. Required number = 27.
Explanation as extracted from the printed page; notation may be imperfect.