A train covers 20 km, 30 km, 60 km and 90 km at speeds of 10 km/h, 15 km/h, 12 km/h and 18 km/h respectively. The average speed of the train for the total journey is:
Answer & explanation
Correct answer: option 4
Total distance = 20 + 30 + 60 + 90 = 200
Total time = \(\frac{20}{10}\) + \(\frac{30}{15}\) + \(\frac{60}{12}\) +\(\frac{90}{18}\)
= 2 + 2 + 5 + 5
= 14
Average speed = \(\frac{Total\;distance}{Total\;time}\)
= \(\frac{200}{14}\)
= \(\frac{100}{7}\)