A car runs first 275 km at an average speed of 50 km/h and the next 315 km at an average speed of 70 km/h. What is the average speed (in km/h) for the entire journey?

59

Distance = Speed × time

Time 1 = \(\frac{275}{50}\) = \(\frac{11}{2}\) hours

Time 2 = \(\frac{315}{70}\) = \(\frac{9}{2}\) hours 

Total time  = \(\frac{11}{2}\) + \(\frac{9}{2}\) = 10 hours

Average speed = \(\frac{275 + 315}{10}\) = \(\frac{590}{10}\)

= 59 km/h