Multiple choice

Average weight of a class is decreased by from 48 Kg to 47 Kg when 16 new students entered in class having average weight of 46.25 Kg. Find the number of students in the class initially. कक्षा का औसत वजन 48 किलो से कम होकर 47 किलोग्राम हो गया जब 16 नए छात्र कक्षा में प्रवेश करते हैं जिनका औसत वजन 46.25 किग्रा. था। प्रारम्भ में कक्षा में छात्रों की संख्या ज्ञात कीजिये।

  1. 8

  2. 24

  3. 30

  4. 12

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

Let n be initial number of students. Initial total weight = 48n. After 16 students join: total weight = 48n + 16 × 46.25 = 48n + 740. New average = (48n + 740)/(n + 16) = 47. So 48n + 740 = 47(n + 16) = 47n + 752. Therefore 48n - 47n = 752 - 740, giving n = 12. Initially there were 12 students.