Question

小明乘手扶电梯,光乘电梯到楼顶要1min,光跑要3min,问他既跑又乘电梯一共要多少时间?急..

Answer 1

设到楼顶距离S；

则,乘电梯速度V1=S/1MIN 跑步速度V2=S/3MIN

既跑又乘电梯的速度V=v1+v2=4S/3;

所以,既跑又乘电梯 需要时间 T=S/(4S/3)=3/4MIN