Question 168351
</pre><font size=4><b>  
this is a right triangle problem so use the pathorean theorem:

{{{a^2+b^2=c^2}}} in this case a is 30 and c is 50 and b is what you are looking for

{{{30^2+b^2=50^2}}}

{{{900+b^2=2500}}}
{{{b^2=1600}}} take sqrt of both sides
{{{highlight(b=40)}}}which is how far the train is from the crossing