Ramesh covers one-fourth of the total distance at 30 km/hr, one-fourth at 20 km/hr and rest of his journey at 60 km/hr. Find Ramesh's average speed for the whole distance?
Answer & explanation
Correct answer: option 3
Let the total distance = 120 km. (Multiple of 4, 20, 30, 60)
Time taken in 1st one forth distance = \(\frac{\frac{120}{4}}{30}\) = \(\frac{30}{30}\) = 1hr
Time taken in 2nd one forth distance = \(\frac{\frac{120}{4}}{20}\) = \(\frac{30}{20}\) = 1.5 hr
Remaining distance = 120 - 60 = 60 km.
Time taken in rest distance = \(\frac{60}{60}\) = 1 hr
Total time taken = 1 + 1.5 + 1 = 3.5 hrs.
Average Speed = \(\frac{Total\;distance}{total\;time}\) = \(\frac{120}{3.5}\) = 34.28 km/hr