wzniesienie góry oznaczmy punktem C.
v1 <=> predkosc pod góre, v2 <=> predkosc z góry
AC/v1 + BC/v2 = 210 minut <=> AC/v1 + BC/2v1 = 210 minut
AC/v2 + BC/v1 = 240 minut <=> AC/2v1 + BC/v1 = 240 minut
2AC + BC = 420 minut * v1
AC + 2BC = 480 minut * v1
Odejmując stronami orzymuje
BC - AC = 1h * 25km /h = 25 km
BC = 25 km + AC
AC + 2(25km + AC) = 8h * 25k/h = 200 km
AC + 50km + 2AC = 200km
3AC = 150km
AC = 50 km
BC = 75 km
AB = 125 km.