Practicing Success
A train started from A to B with a speed of 20 km/h , then from B to C (where BC = 2AB) with a speed of 60 km/h , and returns from C to A with a speed of 10 km/h. What is the average speed (in km/h) of the train during the entire journey ? |
\(\frac{320}{23}\) \(\frac{80}{3}\) \(\frac{360}{23}\) \(\frac{60}{23}\) |
\(\frac{360}{23}\) |
Total distance = x + 2x + 3x Distance = Speed × Time Total time = \(\frac{x}{20}\) + \(\frac{2x}{60}\) + \(\frac{3x}{10}\) = \(\frac{23x}{60}\) Avg. speed = \(\frac{Total\;Distance}{Total\;Time\;Taken}\) = \(\frac{x \;+\; 2x\; +\; 3x}{\frac{23}{60}}\) = \(\frac{360}{23}\) |