10 km

Set the level road to be x kilometers and the slope to be y kilometers, and walk five times with * * *, which requires the actual calculation of xy value and x+y knot.

Topic 2

6.25 meters

Suppose it takes x seconds to know 80/x of two speeds.

75/x； Just finished running 100 meters, divide 80/x by h= 100.

Running in the same room

：

H divided by 75/x

Reduce the running distance with 100.