The average age of a class of 12 students is 8 yrs. if the teacher's age is also included, the average increases by one year. Find the age of the teacher\nOptions:\n(A) 30 Years\n(B) 31 Years\n(C) 21 Years\n(D) 34 Years\n(E) 49 Years Stream of consciousness first, then make a decision:
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Total age of students is 12X8 = 96 Years\nTotal age inclusive of teacher = 13X (8+1) = 117\nSo, Teacher's age is 117-96 = 21 Yrs\nThere is a shortcut for these type of problems\nTeacher's age is 8+(13X1) = 21 Years
Thus, the answer is (C).
Assistant