There are 15 students in a class. Their average weight is 40 kg. When one student leaves the class, the average weight is 39.5 kg. What is the weight of the student who left the class (where kg means kilogram)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 47 kg.
Number of students = 15
The average weight of students = 40 kg
The total weight of all 15 students is:
Total weight of 15 students = Average weight × Number of students = 40 × 15 = 600 kg
When one student leaves the class:
Number of students = 14
The average weight of students = 39.5 kg
Total weight of 14 students = Average weight × Number of students = 39.5 × 14 = 553 kg
Weight of the student who left = 600 kg − 553 kg = 47 kg