40' = 2/3h
Theo đề: \(v_1=1,25v_2\)
\(v_2\cdot\dfrac{2}{3}+6=v_1\cdot\dfrac{2}{3}\)
\(\Leftrightarrow v_2\cdot\dfrac{2}{3}+6=1,25v_2\cdot\dfrac{2}{3}\Leftrightarrow\dfrac{1}{6}v_2=6\Leftrightarrow v_2=36\left(km/h\right)\)
\(\Rightarrow v_1=1,25v_2=36\cdot1,25=45\left(km/h\right)\)