一火車以60km/hr的速率....則火車全程之平均速率為?

路程: 60*2+40*1+55*(5-2-1)=270km=270000m
(走完全程<共>費時5小時)
時間: 5hr=5*60min=5*60*60s=18000s
Asn:270000/18000=15m/s

60km x 2hrs = 120km
40km x 1hr = 40km

5 - 2 - 1 = 2

so
55km x 2hr = 110km

120 + 40 + 110 = 270km

= 270000 / ( 5 x 60 x 60 )
270000 / 18000 = 15

15 meter per sec

共走 60 * 2 + 40 * 1 + 55 * 5 = 435 km = 435000 m (表示共走里程)
435000 / ((2 + 1 + 5) * 3600) = 15.10416667

大概15m/s吧

用心算 冏