A person traveled 30% of a distance with a speed of 90 km/h and the remaining with a speed of 140 km/h .  What is his average speed for the whole journey in km/h ?

120

Let the total distance = 100 km

30% of a distance = 30 km

Distance = Speed ×  Time

Total time = \(\frac{30}{90}\) + \(\frac{70}{140}\) 

                = \(\frac{5}{6}\)           

Avg. speed = \(\frac{Total\;distance}{Total\;time\;taken}\)

Avg. speed = \(\frac{100}{\frac{5}{6}}\) = 120 km/h