Question 670468
They are moving apart at the sum of their speeds
Let {{{ s }}} = the speed of the second plane
{{{ s - 40 }}} = the speed of the 1st plane
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{{{ 250 = ( s + s - 40 )*2 }}}
{{{ 250 = 4s - 80 }}}
{{{ 4s = 330 }}}
{{{ s = 82.5  }}}
{{{ s - 40 = 82.5 - 40 }}}
{{{ s - 40 = 42.5 }}}
the slower plane is flying at 42.5 mi/hr
check:
{{{ 250 = ( s + s - 40 )*2 }}}
{{{ 250 = ( 82.5 + 42.5 )*2 }}}
{{{ 250 = 125*2 }}}
{{{ 250 = 250 }}}
OK