A car travels 120 km at 40 km/h, 120 km at 60 km/h, and 100 km at 80 km/h. What is the average speed of the car for the whole journey?
54.4 km/h
Time for each leg: \(\tfrac{120}{40}=3\) h, \(\tfrac{120}{60}=2\) h, \(\tfrac{100}{80}=1.25\) h.
Total distance: \(120+120+100 = 340\) km. Total time: \(3+2+1.25 = 6.25\) h.
Average speed: \(\dfrac{340}{6.25} = 54.4\) km/h.
Hence, the average speed of the car for the whole journey is 54.4 km/h.
A car runs first 275 km at an average speed of 50 km/h and the next 315 km at an average speed of 70 km/h. What is the average speed ( in km/h) for the entire journey?
Akhil rides first 12 km at a speed of 16 km/h and further 6 km at a speed of 20 km/h. Find his average speed (in km/h).
Shyam drives his car 30 km at a speed of 45 km/h and, for the next 1 h 20 m, he drives it at a speed of 51 km/h. Find his average speed (in km/h) for the entire journey.
X and Y travel a distance of 90 km each such that the speed of Y is greater than that of X. The sum of their speeds is 100 km/h and the total time taken by both is 3 hours 45 minutes. The ratio of the speed of X to that of Y is:
If a man travels at \(\frac{1}{x}\) km/h on a journey and returns at \(\rm \frac{1}{x^2}\) km/h, then his average speed for the journey is: