la urcare l=vuxtu, lungimea pantei, vu viteza la urcare, tu timpul la urcare
12min si 30 sec=12,5 min=12,5/60 h
la coborire l=vcx(tu-12,5/60) deci
vuxtu=vcxtu-vcx12,5/60
15xtu=40tu-40x12,5/60 numitor comun 60
900tu=2400tu-500
1500tu=500
tu=500/1500=1/3h=20 min
l=vuxtu=15x1/3=15/3=5 km
verificare tc=l/vc=5/40=0,125h=0,125x60=7.5 min
