2012 · Q97
The mean weight of 150 students in a class is 60 kg. The mean weight of boys is 70 kg and that of girls is 55 kg. What is the number of boys in the class?
Elementary MathematicsStatistics
- A50
- B60
- C75
- D100
Explanation
70b+55(150-b) = 9000 gives b = 50.