The fast train and the slow train leave each other from a and B. the fast train takes one fifth of the whole journey first, and then the slow train leaves 11 kilometers later. When they meet, the slow train makes the whole scene Two out of seven are known to have a speed ratio of 5 to 4

The fast train and the slow train leave each other from a and B. the fast train takes one fifth of the whole journey first, and then the slow train leaves 11 kilometers later. When they meet, the slow train makes the whole scene Two out of seven are known to have a speed ratio of 5 to 4

If the fast train speed is 5xkm / h, the slow train speed is 4xm / h, and the slow train departure time is a hour, then the distance between a and B is
4x*a/(2/7)=14xa km,
Then: (5x + 4x) a + (1 / 5 * 14xa + 11) = 14xa
9xa+14xa/5+11=14xa
14xa/5+11=5xa
14xa+55=25xa
xa=5 km
14xa=5*14=70 km
That is, the distance between a and B is 70km