The average age of a class of 39 students is 15 years. If the age of the teacher be included, then the average increases by3 months. Find the age of the teacher.  Choose the correct choice from the following answers:
A) 20	B) 23	C) 25	D) 21	E) 22
Total age of 39 persons = (39 x 15) years   = 585 years.   Average age of 40 persons= 15 yrs 3 months   = 61/4 years.   Total age of 40 persons = (61/4 )x 40) years= 610 years.   :. Age of the teacher = (610 - 585)= 
<gadget id="calculator">(610 - 585)</gadget>
<output>25</output>
25 years.   Answer is 25.
<result>C</result>
The average age of a class of 39 students is 15 years. If the age of the teacher be included, then the average increases by3 months. Find the age of the teacher.