2010 · Q80
The mean weight of 150 students in a certain class is 60 kg. The mean weight of the boys from the class is 70 kg, while that of girls is 55 kg. What is the number of girls in the class?
Elementary MathematicsStatistics
- A105
- B100
- C95
- D60
Explanation
70b+55(150-b)=9000 gives b=50, girls=100.