Mr. Smith calculated the average of 10 three digit numbers. But due to a mistake he reversed the digits of a number and thus his average increased by 39.6 The difference between the unit digit and hundreds digit of that number is : Answers: A) 2 B) 4 C) 5 D) 6 E) 7
Since the average increased by 39.6 and there were a total of 10 numbers, it means the incorrect number was 39.6 greater than the correct number.   Say, the correct number was abc (where a, b and c are the digits of the 3 digit number)   Then the incorrect number was cba.   100c + 10b + a - (100a + 10b + c) = 396   99c - 99a = 99(c - a) = 396   99*4 = 99(c - a)   So c - a = 4   Answer (4)
<result>B</result>
Mr. Smith calculated the average of 10 three digit numbers. But due to a mistake he reversed the digits of a number and thus his average increased by 39.6 The difference between the unit digit and hundreds digit of that number is :