SOLUTION: A trip of 500 kilometres took five and a half hours to complete by car. During the first 30 minutes, travelling was slow because of heavy traffic, but for the rest of the journey,

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Question 1196500: A trip of 500 kilometres took five and a half hours to complete by car. During the first 30 minutes, travelling was slow because of heavy traffic, but for the rest of the journey, the car's speed was 10km/hr, less than twice the car's speed in heavy traffic. Determine the speed of the car in heavy traffic.
Found 2 solutions by ikleyn, josgarithmetic:
Answer by ikleyn(52781)   (Show Source): You can put this solution on YOUR website!
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Let x be the slow speed (in heavy traffic), in kilometers per hour.

Then the faster speed was (2x-10) kilometers per hour, according to the problem.


Now write the total distance equation

    0.5x + 5*(2x-10) = 500.    (Here 0.5 represents 0.5 hour = 30 minutes).


Simplify and find x

    0.5x + 10x - 50 = 500

       10.5x         = 500 + 50 = 550

          x                    = 550/10.5 = 52.381 km/h.

ANSWER.  The average speed in slow traffic was 52.381 km/h.

Solved.

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Answer by josgarithmetic(39617)   (Show Source): You can put this solution on YOUR website!
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                            SPEEDS         TIME(hours)    DISTANCES

Slow in Heavy Traffic          r             0.5          0.5r

Rest of Journey              2r-10           5            5(2r-10)

TOTAL                                        5.5           500


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