Question 397193
How far does the 1st train get in 10 min?
{{{d[1] = 40*(1/6)}}} (10 min is 1/6 of an hour)
{{{d[1] = 20/3}}} km
Now if the 2nd train has to travel {{{d}}} km to
meet the 1st train, then the 1st train has to
travel {{{d - 20/3}}} km
They will both travel for the same time period
1st train:
(1) {{{d - 20/3 = 40t}}}
2nd train:
(2) {{{d = 60t}}}
Substitute (2) in (1)
{{{60t - 20/3 = 40t}}}
{{{180t - 20 = 120t}}}
{{{60t = 20}}}
{{{t = 1/3}}} hr
They will meet 20 min after the 2nd train leaves
check answer:
(2) {{{d = 60t}}}
{{{d = 60*(1/3)}}}
{{{d = 20}}} km
and
(1) {{{d - 20/3 = 40t}}}
{{{20 - 20/3 = 40*(1/3)}}}
{{{60 - 20 = 120*(1/3)}}}
{{{40 = 40}}}
OK