设扶梯速度x,小华速度y,则小明速度2y,扶梯可见L阶
花费时间:
小华:L/(x+y) = 14/y
小明:L/(x+2y) = 21/2y
两式相除:
(x+2y)/(x+y) = 4/3
3(x+2y)= 4(x+y)
x = 2y
代入小华的时间:
L/(x+y) = 14/y
L/3y = 14/y
L = 42阶
设扶梯速度x,小华速度y,则小明速度2y,扶梯可见L阶
花费时间:
小华:L/(x+y) = 14/y
小明:L/(x+2y) = 21/2y
两式相除:
(x+2y)/(x+y) = 4/3
3(x+2y)= 4(x+y)
x = 2y
代入小华的时间:
L/(x+y) = 14/y
L/3y = 14/y
L = 42阶