UPSC Prelims 2020·CSAT·Quantitative Aptitude·Arithmetic

The average age of a teacher and three students is 20 years. If all the three students are of same age and the difference between the age of the teacher and each student is 20 years, then what is the age of the teacher?

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Last updated 23 May 2026, 3:31 pm IST
  1. A25
  2. B30
  3. C35Correct
  4. D45

Explanation

Let the age of each student be x years. Since the teacher is 20 years older than each student, the teacher's age is x + 20. Total number of people = 4 (one teacher + three students). The average age is 20 years, so the sum of all ages is 4 × 20 = 80. Sum equation: (x + 20) + 3x = 80 4x + 20 = 80 4x = 60 x = 15. Each student is 15 years old, and the teacher is 15 + 20 = 35 years. Therefore, the answer is C (35).
Quantitative Aptitude: The average age of a teacher and three students is 20 years. If all the three students are of same age and the differenc
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