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The average age of 30 students is 9 years. If the age of their teacher is included, the average age becomes 10 years. The age of the teacher (in years) is
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- 27
- 31
- 35
- 40
- 27
Correct Option: D
Given , The average age of 30 students = 9 years.
Total age of 30 students = 9 × 30 = 270 years
The average age of 30 students and a teacher = 10 years.
Total age of 30 students and a teacher = 31 × 10 = 310 years
Age of the teacher = Total age of 30 students and a teacher – Total age of 30 students
∴ Age of the teacher = 310 – 270 = 40 years
