Multiple choice

The average age of a class of 80 girls was 20 years, the average age of 20 of them was 22 years and that of another 20 was 24 years. Find the average age of the remaining girls. एक कक्षा में 80 लड़कियों की औसत आयु 20 वर्ष थी, उनमें से 20 की औसत आयु 22 वर्ष थी और दूसरे 20 की 24 वर्ष थी । तो शेष बची लड़कियों की औसत आयु क्या है ?

  1. 17 years/वर्ष

  2. 19 years/वर्ष

  3. 21 years/वर्ष

  4. 15 years/वर्ष
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total age of 80 girls = 80 × 20 = 1600 years. First 20 girls: 20 × 22 = 440 years. Next 20 girls: 20 × 24 = 480 years. Remaining 40 girls: 1600 - 440 - 480 = 680 years. Average of remaining = 680/40 = 17 years.

Keep practicing — related questions