9 A family drives 775 km for their holiday. The first part of the trip is 52 km and takes 1 h 10 min. The remainder is covered at an average speed of 100 km/h. Find the average speed for the whole journey.
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Step-by-step explanation:
The average speed of the motorist is 37.5 km/hr.
Step-by-step explanation:
A motorist travels a distance of 150 km and comes back. He goes with an average speed of 50 km per hour and comes back with a speed of 30 km per hour.
Now, the total time taken by the motorist for this return trip is (\frac{150}{50} + \frac{150}{30}) = 3 + 5 = 8(
50
150
+
30
150
)=3+5=8 hours.
And the total distance traveled by the motorist is (150 + 150) = 300 km.
Therefore, the average speed of the whole journey in km per hour will be
= \frac{\textrm {Total distance Traveled}}{\textrm {Total time taken}}
Total time taken
Total distance Traveled
= \frac{300}{8} = 37.5
8
300
=37.5 km per hour. (Answer)
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