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.

(s9 +10a +b)/10= (s9+10b+a)/10 - 1.8

s9 + 10a + b = s9 + 10b + a - 18

10a - a =10b - b - 18

9a = 9b - 18
a = b -2
2 = b - a

Posted by ben on 2003-11-19 09:46:11