Notam lungimea traseului cu x.
In prima zi merge 4/10 * x =2/5 * x
Dupa prima zi mai are de mers x - 2/5 * x = x(1-2/5) = x(5/5-2/5) = x*3/5
A doua zi merge 2/3 din rest, adica 2/3*x*3/5= 2/5*x
Dupa a doua zi mai are de mers x*3/5 - 3*2/5 = x*(3/5-2/5) = x*1/5
In a treia zi merge 2/3 din noul rest, adica 2/3*x*1/5 = 2/15*x
Dupa a treia zi mai are de mers x*1/5 - x*2/15 = x(1/5-2/15) = x(3/15-2/15) = x*1/15
Aceasta distanta = 10 km, adica:
x*1/15 = 10
x = 10 : 1/15 = 10 x 15 = 150 km
Lungimea traseului este de 150 km.