Sachin covers half of his journey at 12 km/h and the remaining half at 3 km/h. His average speed is:
4.8 km/h
When equal distances are covered at two different speeds, the average speed is given by the harmonic mean formula \(\text{Average speed} = \frac{2v_1v_2}{v_1+v_2}\).
Here \(v_1 = 12\) km/h and \(v_2 = 3\) km/h, so the average speed is \(\frac{2 \times 12 \times 3}{12+3} = \frac{72}{15}\).
Simplifying, \(\frac{72}{15} = 4.8\).
Hence, the answer is 4.8 km/h.
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Important Questions from Average Speed
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:
