31 vote
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?
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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?
1). 39 years
2). 41 years
3). 40 years
4). 44 years
2 answers
22 vote
41 years : option 2 is the correct answer
31 vote
Solution :
Let us take the teacher's age as 'x'
Given :
●Average age of 19 boys = 21
(Total age of 19 boys ) / 19 = 21
Total age of 19 boys = 21 × 19 = 399
●Average age of 19 boys with their teacher included = 22
(Total age of 19 boys + Teacher's age) / 20 = 22
Total age of 19 boys + Teacher's age = 22 × 20
Total age of 19 boys + Teacher's age = 440
399 + Teacher's age = 440
Teacher's age = 440 - 399
Teacher's age = 41 years
The correct option is 2). 41 years
