At the end of 2005 Walter was half as old as his grandmother. The sum of the years in which they were born is 3860. How old will Walter be at the end of 2006?
Answer
The sum of the ages of Walter and his grandmother at the end of 2005 is 2*2005-3860=150. Since Walter was half as old as his grandmother, Walter was 50 and his grandmother was 100. Therefore, Walter will be 51 at the end of 2006.
