Multiple choice

In a school , the average age of students is 6 years, and the average age of 12 teachers is 40 years. If the average age of the combined group of all the teachers and students is 7 years, then the number of students is :

  1. 396

  2. 400

  3. 408

  4. 416

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let n be the number of students. Total age of students = 6n. Total age of 12 teachers = 12 × 40 = 480. Combined average: (6n + 480) / (n + 12) = 7. Solving: 6n + 480 = 7n + 84, so n = 396. Option A is correct.