9. A car travels a certain distance at a speed of 50 km/h and returns at a speed of 40 km/h. Calculate the average speed for the whole journey.
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Answers
Answer:
YOU SHOULD 2 OPTIONS
1. IN PIC
2.average speed-here the distances are equal,we have the formula of finding average speed when distance is equal as V1*V2/V1+V2. if we substitute the values here we get 50*40/50+40 which gives 200/90=20/9 kmph which when converted into m/s gives 8
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Given :-
A car travels a certain distance at a speed of 50 km/h and returns at a speed of 40 km/h.
To Find :-
Average speed for the whole journey.
Solution :-
Let the distance be x
Total distance = x + x = 2x km
Total time taken
Time in first case = Distance/Speed
Time in first case = x/50
Time in second case = Distance/Speed
Time in second case = x/40
Avg. speed = Total distance/Total time
Avg. speed = 2x/(x/50 + x/40)
Avg. speed = 2x/(4x + 5x/200)
Avg. speed = 2x/(9x/200)
Avg. speed = 2x/9x × 200
Avg. speed = 2/9 × 200
Avg. speed = 400/9 km/h