Boys and girls

If the ratio of male and female teachers is 2:5 and the proportion of male and female students is the same, how many are girls if there are 42 boys?

Final Answer:

g =  30

Step-by-step explanation:

$$\begin{gathered} b:g=2:5=2/5 \\ b+g=42 \\ g\cdot \frac{2}{5}+g=42 \\ g\cdot \frac{7}{5}=42 \\ g=42/\frac{7}{5}=42:\frac{7}{5}=42\cdot \frac{5}{7}=\frac{42\cdot 5}{7}=\frac{210}{7}=30 \end{gathered}$$

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