Good grades

At school, 10 percent of boys and 15 percent of girls achieve good grades. What percentage of students achieve good grades when 60 percent of girls are in school?

Final Answer:

p =  13 %

Step-by-step explanation:

$$\begin{gathered} p_1=10\% \\ {p}_2=15\% \\ {p}_4=60\%=\frac{60}{100}=\frac{3}{5}=0.6\% \\ {p}_3=1-p_4=1-0.6=\frac{2}{5}=0.4\% \\ p=\frac{p_1\cdot p_3+p_2\cdot p_4}{p_3+p_4}=\frac{10\cdot 0.4+15\cdot 0.6}{0.4+0.6}=13\% \end{gathered}$$

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