Xiao Ming's father drove from home to the railway station at the speed of 50 km / h, 15 minutes earlier than the train. If he drove at the speed of 40 km / h, he was 15 minutes later than the train. How fast did he arrive 10 minutes earlier than the train?
50*0.5=25
25/(50-40)=2.5
50*(2.5-0.5)=100
100 / 2.25 = 44.4 km / h
I go to school by bike
I go to school by bike.