题目

英语翻译
You are planning a bicycle trip for which you want to average 24km/h.You cover the first half of the trip at an average speed of 21km/h.What must your average speed be in the second half of the trip to meet your goal?

提问时间：2020-08-07

答案

1.以路程为等量S=24t(T1+T2)
S=21*T1+V2*T2,又S=1/2S+1/2S→→21*T1=V2*T2→→T1=V2*T2/21
所以24t(T1+T2)=21*T1+V2*T2→→3*T1=(V2-24)T2
3*（V2*T2/21)=(V2-24)T2→→3*V2/21=V2-24
V2=28km/h
2.以时间为等量
(S/2)/21 + (S/2)/v2 = S/24
∴ v2 = 28 km/h
因为不会打脚标因此把各个量如SVT本应该是小写的改成大写了,楼主书写的时候可以改成小写的,并把→根据逻辑关系改成∵和∴