The airplane from Prague to Bratislava was flying at a speed of 60 km/h less and back by 70 km/h greater than the original speed. What was the original speed if the plane returned to Prague according to the timetable?

Correct answer:

v =  840 km/h

Step-by-step explanation:

s/(v60)+s/(v+70)=2s/v 1/(v60)+1/(v+70)=2/v v(v+70)+v(v60)=2 (v+70)(v60) 10v=8400 v=8400/10=840 =840 km/h

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