Student instrument percentage

Of the 30 students in the class, two-fifths are boys. A quarter of them are learning to play a musical instrument. 6 girls also play it. What percentage of students in this class do not play any musical instrument?

Final Answer:

p =  70 %

Step-by-step explanation:

$$\begin{gathered} z=30 \\ c=\frac{2}{5}\cdot z=\frac{2}{5}\cdot 30=\frac{2\cdot 30}{5}=\frac{60}{5}=12 \\ d=z-c=30-12=18 \\ h=\frac{1}{4}\cdot c+6=\frac{1}{4}\cdot 12+6=9 \\ p=100\cdot \frac{z-h}{z}=100\cdot \frac{30-9}{30}=70\% \end{gathered}$$

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