Question 1020264
Think of one of them as standing still.
Think of the other one moving at the sum
of their speeds.
Let {{{ t }}} = time in hrs for them to be 8 mi apart
{{{ 8 = ( 4 + 6 )*t }}}
{{{ 8 = 10t }}}
{{{ t = .8 }}}
{{{ .8*60 = 48 }}}
They will be 8 mi apart in 48 min
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check:
{{{ d[1] = 4t }}}
{{{ d[1] = 4*.8 }}}
{{{ d[1] = 3.2 }}}
and
{{{ d[2] = 6t }}}
{{{ d[2] = 6*.8 }}}
{{{ d[2] = 4.8 }}}
and
{{{ d[1] + d[2] = 3.2 + 4.8 }}}
{{{ d[1] + d[2] = 8 }}} mi
OK