A car travels at a constant speed 50km/h for 100km. It then speeds up to 100 km/h and is driven another 100km. What is the car’s average speed for the 200 km trip?
100 km in 2 hr
100 km in 1 hr
---------------------------
200 km in 3 hr = 200/3 = 66 2/3 km/hr
time = distance/speed, so avg speed = totaldistance/totaltime
(100+100)km / (100/50 + 100/100)hr = 200km/3hr = 200/3 km/hr