The average age of class of 20 students is 20 years. If the School principal's age is included the average increases by 1. What is the age of the principal?

31

40

41

42

Avg x Number = Total 20 nos x 20 years = 400 ...(1) 21 nos x 21 years = 441 ...(2) Principal's age = (2) - (1) = 441 - 400 = 41 years.

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