Question 1167538
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A car travels 20kph faster than a truck. The car covers 480km in two hours less than 
the time it takes the truck to travel the same distance. How fast does the car travel?
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<pre>
Let x be the rate of the car, in miles per hour.

Then the rate of the truck is (x-20) mph.


The time for the car   to travel 480 km is  {{{480/x}}}  hpurs.

The time for the truck to travel 480 km is  {{{480/(x-20)}}}  hours.



The "time" equation is

   {{{480/(x-20)}}} - {{{480/x}}} = 2  hours.



You can solve this equation mentally by easy guess the answer  x= 80.


Indeed,  {{{480/(80-20)}}} - {{{480/80}}} = {{{480/60}}} - {{{480/80}}} = 8 - 6 = 2 hours.



Alternatively, you can solve equation (1) algebraically.

If you do it this way your first step is to multiply both sides by x*(x-20).


<U>ANSWER</U>.  The car's rate is 80 km/h.
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Solved.