Question 877648
RT=D  rate, time, distance.


Distance is unknown.
Let d = journey distance.
{{{40*x=d/2}}} and {{{100*y=d/2}}} using x and y as the times for first half and second half of the journey distance.  ALSO, {{{x+y=40/60}}}, since we could or should keep in units of time as hours.


{{{40x=100y}}}
{{{4x=10y}}}
{{{2x=5y}}}, from the R, T, D reationships.
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{{{x+y=2/3}}}, simplified form of the given time sum.
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Solve the system for x and y:
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{{{highlight_green(2x=5y)}}} AND {{{highlight_green(x+y=2/3)}}}
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When you know x and y, which are in HOURS, you can then find the journey's distance.