A car travels from city A to city B covering a total distance of 360 km under the following conditions, first 100 km covered at a speed of 50 km/h, next 80 km is covered at a speed of 40 km/h, then the car stops for 30 minutes. After that it covers 90 km distance at a speed of 60 km/h and the remaining distance it covers at a speed of 75 km/h. What is the average speed of the car for the entire journey including stoppage time?
50 km/h
Average speed for a journey = total distance ÷ total time, where the total time includes the stoppage time.
Times: 100 km at 50 km/h = 2 h; 80 km at 40 km/h = 2 h; stop = 30 minutes = 0.5 h; 90 km at 60 km/h = 1.5 h.
Remaining distance = 360 – (100 + 80 + 90) = 90 km, covered at 75 km/h in \(\frac{90}{75} = 1.2\) h.
Total time = 2 + 2 + 0.5 + 1.5 + 1.2 = 7.2 h, so the average speed = \(\frac{360}{7.2} = 50\) km/h.
Check: at 50 km/h for 7.2 h the car would cover 50 × 7.2 = 360 km, which equals the total distance from city A to city B.
Hence, 50 km/h.
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Important Questions from Average Speed
A person covers a certain distance at the speed of 60 kmph and returns to the starting point at a speed of 40 kmph . Find the average speed (in km/hour) of the person for the whole journey.
Kapil travels for 4.5 hours at a speed of 50 km / h and 7.5 hours at a speed of 70 km / h. At the end of it, he finds that he covered only 6/7 of the total distance. At what average speed should he travel so that the remaining distance traveled in 5 hours?
A car has to cover 125 kms in 5 hours. What will be the average speed of the car if it has covered 90 kms in the first 3 hours?
A scooter from P to Q travels at 40 km/h and from Q to P at 30 km/h. What is the average speed of the scooter?
A car covers a distance of 100 km at a speed of 60 km/h and another 200 km at a speed of 75 km/h, what is the average speed of the car in km/h for the whole journey? (correct to one decimal place)
