某人跑步，每分钟$$300$$米，$$3$$小时跑完．假设他提速到每分钟$$360$$米，跑完全程比之前节省几分钟？  $$300\times 180\div 360=150$$分钟，$$180-150=30$$分钟． 
(2016 Math League, Grade3）  Running Man is running a certain distance at a constant speed of $$300$$m/min and can finish the entire distance in $$3$$ hours. If he ran at a constant speed of $$360$$m/min, how many minutes less would it take him to run this distance?  Running Man是以$300$ m/min的恒定速度跑完一段距离，可以在$3$小时内跑完全程$$.$$ 如果以以$360$ m/min的恒定速度跑完这段距离会少花多少分钟? 
1: $$30$$ 
2: $$150$$ 
3: $$180$$ 
4: $$360$$ 