A boy was asked to calculate the arithmetic mean of ten positive integers each of which had 2 digits.
By mistake, he interchanged the two digits, a & b, in one of these ten integers. As a result, his answer for the arithmetic mean was 1.8 more than what it should have been.
Find the value of b-a.

If the mean is off by 1.8, and it is the mean of 10 numbers, then the transposed number is off by 18 (10 x 1.8 = 18). So, find any two digit number that, when the digits are reversed, is 18 more than it was before. (13, 24, 35, 46, ...). Looking at these, b-a = 2.

Posted by Andy on 2003-11-19 11:11:43