1.设火车长度为L,速度为V
则:
1000 + L = V * 60
1000 - L = V * 4
V = 31.25m/s
L = 875m
2.m = 1/2
m²+m = 0.75
2m²+2m-1=0.5
3.D
4.设学校距机场距离为S,乘公车到的时间为t
则:
(2/3)S / 30 = t
(2/3)S / 60 = t - 1/6 (10分钟 = 1/6 小时)
t = 1/3 = 20分钟
S = 15 km
1.设火车长度为L,速度为V
则:
1000 + L = V * 60
1000 - L = V * 4
V = 31.25m/s
L = 875m
2.m = 1/2
m²+m = 0.75
2m²+2m-1=0.5
3.D
4.设学校距机场距离为S,乘公车到的时间为t
则:
(2/3)S / 30 = t
(2/3)S / 60 = t - 1/6 (10分钟 = 1/6 小时)
t = 1/3 = 20分钟
S = 15 km