The average age of a class of 20 students is 21 years. The average increased by 1 when the teacher's age also included. What is the age of the teacher? Select:	A) 40	B) 41	C) 42	D) 45	E) 43
Total age of all students =20Ã—21   Total age of all students + Age of the teacher =21Ã—22   Age of the teacher   =21Ã—22âˆ’21Ã—20=21(22âˆ’20)=21Ã—2=42   Answer is 42.
<result>C</result>
The average age of a class of 20 students is 21 years. The average increased by 1 when the teacher's age also included. What is the age of the teacher?