Try this

来源: 于 2009-02-01 21:55:10 [旧帖] [给我悄悄话] 本文已被阅读：次

A speed Va=1000/T (T=time used fot first race)b=
B speed Vb=(1000-50)/T=950/T

For second race:

A time Ta =1050/Va=1050T/1000
B Time Tb=1000/Vb=1000T/950