Question

During first half of a journey a body travel with the speed of 40 km/h and in the next half travels with the speed of 20 km per hour calculate the average speed of full journey

Answer 1

Let the distance traveled in the complete journey be 2x meters.

Speed for the first "x" distance = 40 km/h

Time taken to cover initial "x" distance = $\(\frac{x}{40}\)$ h

Speed for the next "x" distance = 20 km/h

Time taken to cover next "x" distance = $\(\frac{x}{20}\)$ h

Hence, the total time of the journey = $\(\frac{x}{20}\)+\(\frac{x}{40}\)$ h

Total time taken = $\(\frac{3x}{40}\)$ h

Average speed = $\(\frac{2x}{\frac{3x}{40}}\)$

Average speed = $\(\frac{80}{3} \frac{km}{h}\)$

Hence, the average speed for the entire journey is $\(\frac{80}{3} \frac{km}{h}\)$.