Question 811795
The truck's head start is {{{ 60*1.5 = 90 }}} mi
Let {{{ t }}} = the driving time for the car when
it is {{{ 50 }}} mi ahead of the truck
Let {{{ d }}} = the distance the car travels
when it meets the truck
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Equation for truck:
(1) {{{ d - 90 = 60t }}}
Equation for car:
(2) {{{ d = 70t }}}
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By substitution:
(1) {{{ 70t - 90 = 60t }}}
(1) {{{ 10t = 90 }}}
(1) {{{ t = 9 }}}
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In 9 hrs they meet
From the place where they meet, let
the car go {{{ d[2] }}} mi, and the
truck go {{{ d[2] -50 }}}
Let {{{ t[2] }}} = the time to do this
truck's equation:
(1) {{{ d[2] - 50 = 60t[2] }}}
car's equation:
(2) {{{ d[2] = 70t[2] }}}
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(1) {{{ 70t[2] - 50 = 60t[2] }}}
(1) {{{ 10t[2] = 50 }}}
(1) {{{ t[2] = 5 }}}
{{{ t + t[2] = 9 + 5 }}}
It takes 14 hrs for the car to get 50 mi ahead 
of the truck