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?

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.