The cruise ship

The cruise ship speeds 12 km/h at a calm surface. When we sailed 45 km along the river and 45 km back, it took us exactly 8 hours. Which (constant) speed of flow of the river?

Correct answer:

v =  3 km/h

Step-by-step explanation:

45 = t1(12+v) 45 = (8t1) (12v) t1 = 45 / (12+v) 45 = (845/(12+v)) (12v)  45 (12+v)=(8 (12+v)45) (12v)  45 (12+v)=(8 (12+v)45) (12v) 8v272=0 8=23 0 72=2332 GCD(8,0,72)=23=8  v29=0 v1,2=±9=±3 v1=3 v2=3  v>0 v=v1=3=3 km/h t1=45/(12+v)=45/(12+3)=3 h t2=45/(12v)=45/(123)=5 h

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