Question 163033
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When Train B passed the station At 1:32am, how far is Train A since it passed the station earlier at 1:20am? Let's see the distance of Train A:
Remember: {{{Speed=distance/time}}}-----> working eqn
We get via working eqn,
{{{d[A]=S[A]t[A]}}}
What will be {{{t[A]}}}?
The difference when Train B and Train A passed the station:
Difference: 12mins---{{{system(1:32,-1:20)}}}
So,{{{d[A]=80(mi/cross(hr))(12cross(min))(1cross(hr)/60cross(min))}}}
{{{highlight(d[A]=16miles)}}}, Take note of this. This is how far Train A was when Train B passed the station by 1:32am.
.
In finding for {{{time}}}, remember too {{{d[A]=d[B]}}} since they're travelling on both directions. Via working eqn,
{{{d[A]=d[B]}}}
{{{S[A](t)+highlight(16)=S[B](t)}}} . Take note highlighted, we need to add 16miles because Train A was already ahead that much, being ahead 12 minutes remember?
Continuing,
{{{80t+16=90t}}}
{{{16=90t-80t}}}
{{{16=10t}}} ---> {{{cross(16)1.6/cross(10)=cross(10)t/cross(10)}}}
{{{t=(1.6cross(hrs))(60min/1cross(hr))=96mins}}} = 1hr &36mins
Therefore,
{{{highlight(3:08am)}}} ---{{{system(1:32am,+1:36)}}}
This is the time when Train A & Train B will be on the same distance.
In doubt? Go back working eqn,
{{{d[A]=80*1.6+16miles=144miles}}}
{{{d[B]=90*1.6=144miles}}}
{{{d[A]=d[B]}}} right?
Thank you,
Jojo</pre>