Amol was asked to calculate Arithmetic mean of 10 positive integers, each of which had 2 digits. By mistake, he interchanged the 2 digits, say a and b,in one of these 10 integers. As a result, his answer for the Arithmetic mean was 1.8 more than what it should have been. Then b - a equals	Choose the correct choice from the following answers
A) 1 B) 2 C) 3 D) 4 E) None of these
Explanation :   Arithmetic mean is more by 1.8 means sum is more by 18.   So, ba – ab = 18.   b &gt; a because sum has gone up, e.g. 31 – 13 = 18.   Hence, b – a = 2.   Answer : 2
<result>B</result>
Amol was asked to calculate Arithmetic mean of 10 positive integers, each of which had 2 digits. By mistake, he interchanged the 2 digits, say a and b,in one of these 10 integers. As a result, his answer for the Arithmetic mean was 1.8 more than what it should have been. Then b - a equals