The average age of 19 boys in a class is 21 years. If the teacher's age is included, the average increases to 22 years. What is the teacher's age?
39 years
41 years
40 years
40 years
B.
41 years
Let the teacher's age = x years
According to the question,
19 x 21 + x = 20 x 22
399 + x = 440
x = 41 years
