MHB I just want to know one divergent formula

[justone]

Hello. I asked my professor and he couldn't figure it out. If train A and B leave the same point at the same time, A traveling 60mph, B traveling 75mph, how long will it take for B to have traveled twice as far as A?

 

[MarkFL]

Hello. I asked my professor and he couldn't figure it out. If train A and B leave the same point at the same time, A traveling 60mph, B traveling 75mph, how long will it take for B to have traveled twice as far as A?

Train B is traveling 5/4 as fast as train A. If they depart at the same time, then train B will always have traveled 5/4 as far as train B...there is no point in time (where $0<t$) for which train B will have traveled twice as far as train A.

I am going to move this thread to our algebra forum, as that is a better fit.

 

[Greg]

Recall that $d=st$, where $d$ is distance, $s$ is speed and $t$ is time.

With the speeds of train A and train B denoted as $s_1$ and $s_2$ respectively, we must have

$s_2t=2s_1t\implies s_2=2s_1$, but this is clearly not true.