Question

Mình cần lời giải chi tiết 

Answer 1

Theo đề, ta có:

\(\dfrac{x}{40}-\dfrac{x}{60}=\dfrac{1}{2}\)

hay x=60

Answer 2

\(30ph=\dfrac{1}{2}h\)

\(\left\{{}\begin{matrix}S=v_1.t_1=60.\left(t_2-\dfrac{1}{2}\right)\\S=v_2.t_2=40.t_2\end{matrix}\right.\)

\(\Rightarrow60\left(t_2-\dfrac{1}{2}\right)=40t_2\Rightarrow t_2=\dfrac{3}{2}\left(h\right)\)

\(\Rightarrow S_{AB}=t_2.v_2=\dfrac{3}{2}.40=60\left(km\right)\)