In a class, the average weight of the boys is 65 kg and the average weight of the girls is 45 kg. The average weight of the whole class is 57 kg. What is the ratio of the number of girls to the number of boys in the class?
2:3
Let boys=b, girls=g. \(\dfrac{65b+45g}{b+g} = 57\).
\(65b+45g = 57b+57g \Rightarrow 8b = 12g \Rightarrow \dfrac{g}{b} = \dfrac{8}{12} = \dfrac23\).
Hence, the ratio of the number of girls to the number of boys is 2:3.
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