The average weight of some students in a class was 69.5 kg. When 10 students of average weight 68 kg joined the class, and 6 students of average weight 60 kg left the class, it was noted that the average weight of the new group of students increased by 2 kg. How many students are there in the class now?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is Option 2 i.e. 21.
Concept Used:
Total weight = Average weight × Number of students
Explanation:
Let the number of students be x.
Sum of weights of all students = x × 69.5 = 69.5x kg
According to the given question,
69.5x + (68 × 10) - (60 × 6) = 71.5(x + 10 - 6)
⇒ 69.5x + 680 - 360 = 71.5x + 715 - 429
⇒ 2x = 34
⇒ x = 17
New number of students = 17 + 10 - 6 = 21
Hence the required answer is 21.