(1)設(shè)上山的速度為Xkm/h,上山下山的路程一樣,則有方程：2.4*X=（4-2.4）*(X+0.5)解得：X=1則山路長(zhǎng)為：S=2.4*1=2.4(km)(2)平均速度等于總路程除以總時(shí)間所以平均速度V=2.4*2/4=1.2(h)????????÷??????????????2.4H???????????4H?????????????? T2=4H-2.4H=1.6H???????V?????????V+0.5?????S1=S2????????S=VT?? 2.4V=1.6*(V+0.5)???V=1km/h?????????????V+0.5km/h=1km/h+0.5km/h=1.5km/h?????S=VT?????·????S1+S2??S=2.4h*1km/h+1.5km/h*1.6h=2.7km?????V=(S1+S2)/(t1+t2)???????????V=??2.4km+2.7km??/(2.4h+1.6h)=1.25km/h{???????????????????ù??????}