Question 162289
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Remember: {{{Speed=distance/time}}}, Working eqn
We 1st calculate the distance {{{d[1]}}} travelled of TR[1] after 3 hours:
Via working eqn,
{{{S[1]=d[1]/t[1]}}}
{{{d[1]=S[1]t[1]=80*3=240km}}}
After 3 hours, {{{t[1]=t[2]}}}, via working eqn we get
{{{t[1]=d[1]/S[1]}}} ----------------> EQN 1
{{{t[2]=d[2]/S[2]}}} ---------------->EQN 2
{{{EQN1=EQN2}}}
{{{d[1]/S[1]=d[2]/S[2]}}}
{{{240/80=d[2]/120}}}
{{{3=d[2]/120}}}
{{{highlight(d[2]=360km)}}}. Why highlighted? we'll see below:
.
how long it took {{{TR[2]}}} to travel 360km? Via EQN 2,
{{{t[2]=360/120=3hours}}}
In this span of ANOTHER 3 hours, how far {{{TR[1]}}} travelled? Via EQN 1,
{{{t[1]=(d[2]-d[1])/S[1]}}}
{{{t[1]=(360-240)/80=120/80=1.5hrs}}}
So, total time travlled by {{{TR[1]=3hrs+1.5hrs=4.5hrs}}}; 
So Total Distance travlled by {{{TR[1]}}} in 4.5 hrs:
via working eqn,
{{{d[1.1]=S[1]t[1.1]=80*4.5}}}
{{{highlight(d[1.1]=360km)}}}. SEE highlighted, both are the same, and we'll meet at this distance. 
Hope this helps.
Thank you,
Jojo</pre>