The average age of a group of 10 persons was decreased by 3 years when one person, whose age was 42 years, was replaced by a new person. Find the age of the new person?
Choose the correct choice.
A) 18  B) 56  C) 12  D) 17  E) 14
Initial average age of the 10 persons be P.   Age of the new person Q.   Sum of the ages of the initial 10 persons = 10P   New average   = (P-3) 10(P-3)   = 10P - 42 + Q   =&gt; Q = 12   Answer:12
<result>C</result>
The average age of a group of 10 persons was decreased by 3 years when one person, whose age was 42 years, was replaced by a new person. Find the age of the new person?