Question 171435
d=rt.   we know the distance in both cases is 50. Lets call the local trains rate r and its time t.  So the express's rate would be 2r and its time t-1
:
50=rt..........eq 1
50=2r(t-1).....eq 2
:
lets rewrite eq 1 as t=50/r and plug that value into eq 2
:
{{{50=2r((50/r)-1)}}}----->{{{50=2r((50-r)/r)}}}----
{{{50=2cross(r)(50-r)/cross(r)}}}
{{{50=100-2r}}}---->{{{-2r=-50}}}
{{{highlight(r=25)}}}MPH-speed of the local train
{{{highlight(2(25)=50)}}}MPH-speed of the express
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