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A man covered one-third part of a journey at the speed of 50 km/hr , one-fourth part of the journey at the speed of 40 km/hr and rest part of the journey at the speed of 20 km/hr . Find his average speed (in km/hr) during the whole journey . |
28\(\frac{19}{81}\) 25 26\(\frac{13}{17}\) 29\(\frac{17}{27}\) |
29\(\frac{17}{27}\) |
Let the total distance be 2400 kms
Time taken for first one third distance = \(\frac{800}{50}\) = 16 hr
Time taken for first one fourth distance = \(\frac{600}{40}\) = 15 hr
Remaining distance = 2400 - 1400 = 1000 kms
Time taken for last 1000 kms = \(\frac{1000}{20}\) = 50 hr
Average speed = \(\frac{total \; distance }{total \; time }\)
= \(\frac{2400}{81}\) = 29\(\frac{17}{27}\) km/hr |
