l_1=\frac{U_1}{3}=\frac{15}{3}=5\\\\l_2=t_2*U_2=>t_2=\frac{2U_2}{3}=\frac{2*45}{3}=30\\\\U=\frac{5+30}{\frac{1}{3}+\frac{2}{3} }=35" alt="U=\frac{l_1+l_2}{t_1+t_2}\\\\l_1=t_1*U_1=>l_1=\frac{U_1}{3}=\frac{15}{3}=5\\\\l_2=t_2*U_2=>t_2=\frac{2U_2}{3}=\frac{2*45}{3}=30\\\\U=\frac{5+30}{\frac{1}{3}+\frac{2}{3} }=35" align="absmiddle" class="latex-formula">
Ответ: 35 м/с