Question 937727
to make things easy, you can think of this as 
one person standing still and the other traveling
at the sum of their speeds from A to B
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Let {{{ t }}} = time in hrs until they meet
{{{ 100 = ( 100 + 50 )*t }}}
{{{ 100 = 150t }}}
{{{ t = 100/150 }}}
{{{ t = 2/3 }}}
{{{ (2/3)*60 = 40 }}}
They will meet in 40 min
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check:
Lucia's equation:
{{{ d[1] = 100t }}}
{{{ d[1] = 100*(2/3) }}}
{{{ d[1] = 200/3 }}}
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Jack's equation:
{{{ d[2] = 50t }}}
{{{ d[2] = 50*(2/3) }}}
{{{ d[2] = 100/3 }}}
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{{{ d[1] + d[2] = 200/3 + 100/3 }}}
{{{ d[1] + d[2] = 300/3 }}}
{{{ d[1] + d[2] = 100 }}}
OK