document.write( "Question 815732: Two trains with lengths 120m and 80m are moving with velocities 42kmph and 30kmph in opposite directions . Find the time they will completely cross each other. \n" ); document.write( "

Algebra.Com's Answer #491173 by josmiceli(19441) $\"\"$ $\"About$

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Think of one train as moving at the sum of their
\n" ); document.write( "speeds and the other train standing still.
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\n" ); document.write( "Now picture the moment when the leading edges
\n" ); document.write( "( the engines ) of each train meet.
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\n" ); document.write( "Now imagine you are at the very tail end of the
\n" ); document.write( "moving train. You will have to travel the length
\n" ); document.write( "of your train until you are at the engine of the
\n" ); document.write( "stationary train, and then you will have to travel
\n" ); document.write( "the length of the stationary train also until
\n" ); document.write( "both tail ends meet, and the trains have passed
\n" ); document.write( "each other.
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\n" ); document.write( "You can write the equation for this as:
\n" ); document.write( " $\"+.12+%2B+.08+=+%28+42+%2B+30+%29%2At+\"$
\n" ); document.write( "where units are km for distance and hrs for time
\n" ); document.write( " $\"+.2+=+72t+\"$
\n" ); document.write( " $\"+t+=+.002778+\"$ hrs
\n" ); document.write( "To get seconds:
\n" ); document.write( " $\"+.002778%2A360+=+1+\"$ sec\r
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