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?
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?
- A
$50$
- B
$60$
- C
$75$
- D
$100$
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