Question 967353
What is the 1st car's head start?
{{{ d[1] = 56*1 }}}
{{{ d[1] = 56 }}} km
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Start a stopwatch when the 2nd car leaves Hartford
Let {{{ d }}} = distance in km 2nd car travels
until it catches 1st car
Let {{{ t }}} = time in hrs on stopwatch when 2nd
car catches 1st car
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Equation for 1st car:
(1) {{{ d - 56 = 56t }}}
Equation for 2nd car:
(2) {{{ d = 84t }}}
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By substitution:
{{{ 84t - 56 = 56t }}}
{{{ 28t = 56 }}}
{{{ t = 2 }}} hrs
and
(2) {{{ d = 84*2 }}}
(2) {{{ d = 168 }}} 
168 km from Hartford the 2nd car overtakes the 1st
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check:
(1) {{{ d - 56 = 56t }}}
(1) {{{ 168 - 56 = 56*2 }}}
(1) {{{ 112 = 112 }}}
OK