Question 1167193
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The time equation is


    {{{360/r}}} - {{{360/(r+10)}}} = 3  hours.


where "r" is the rate of the slower train.


<U>Answer</U>  which can be guessed mentally is 30 mph.


Alternatively, you can reduce this equation to a quadratic equation and solve it by any method.


First step in this way is to multiply all the terms by r*(r+10) and simplify.


<U>CHECK</U>.  {{{360/30}}} - {{{360/40}}} = 12 - 9 = 3 hours.
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