Question 984869
The sum of the ages of the original group was 
(Number of people)x(average(mean))=(10)(15)=150 years
Adding one person, the sum to have a mean of 14 is 
(Number of people)x(average(mean))=(14)(11)=154 years
154 years-150 years=4 years
ANSWER The 11th person was 4 years old.