[tex]V_r=1 \ dm^3=(10 \ cm)^3=1000 \ cm^3\\\\d_r=2,48 \ \frac{g}{cm^3}\\\\m_r=1000 \ cm^3\cdot2,48 \ \frac{g}{cm^3}=2480 \ g\\\\C_p=5\%\\\\m_s= \ ?\\\\\frac{m_s}{2480g}\cdot100\%=5\% \ \ |:100\%\\\\\frac{m_s}{2480g}=0,05 \ \ |\cdot2480 \ g\\\\m_s=\boxed{124 \ g \ fluorku \ potasu}[/tex]
