Question

Neeraj reaches school in a car at an average speed of 20km/h. While returning; his speed becomes 30km/h due to lesser crowd. What is the average speed of Neeraj's car for the whole journey?



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Answer 1

Answer:

The average speed of Neeraj's car is 24 km/hr

Step-by-step explanation:

Let the given distance be x km

In the whole journey, Neeraj travelled 2x km

In first half, his speed is 20 km

Then, $time\:taken=\frac{distance}{speed}$

$\implies\:time\:taken=\frac{x}{20}\:hours$

In second half, his speed is 30 km

Then,

$\implies\:time\:taken=\frac{x}{30}\:hours$

Total time taken

$=\frac{x}{20}+\frac{x}{30}$

$=\frac{30x+20x}{20*30}$

$=\frac{5x}{2*30}$

$=\frac{x}{2*6}$

$=\frac{x}{12}$

$\therefore\:Average\:speed=\frac{Total\:distance}{Time\:taken}$

$Average\:speed=\frac{2x}{\frac{x}{12}}$

$Average\:speed=\frac{2}{\frac{1}{12}}$

$Average\:speed=24\:km/hr$