Question 970173
Picture the tunnel being quite a bit longer than the train
The problem says the train " takes 5 seconds to enter a tunnel "
I think this means that the end of the train reaches the beginning
of the tunnel in 5 seconds
{{{ 60 }}} mi/hr = {{{ 60/60 = 1 }}} mi/sec
{{{ d = 1*5 }}}
{{{ d = 5 }}} mi
The train is 5 mi long
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The back of the train reaches the other end of the tunnel
in {{{ 40 }}} sec
The head of the train reached the end of the tunnel {{{ 5 }}}
sec before this, or in {{{ 35 }}} sec
{{{ 5 }}} sec later the back of the train reaches
the end of the tunnel
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{{{ 35 + 5 = 40 }}} sec
{{{ d = 1*40 }}}
{{{ d = 40 }}} mi
The tunnel is 40 mi long
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Hopd I got it
and hope this makes sense

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