Math CentralQuandaries & Queries


Question from Victor, a teacher:

A plane flies from Istanbul to Lagos at 800km/h and then returns to Istanbul at 900km/h. The return trip takes 1 hour less than the flight to Lagos. What is the distance between Istanbul and Lagos?

Hi Victor,

Most of these distance-time-rate problems depend on the fact that rate is distance divided by time. Suppose the distance between Istanbul and Lagos is $d$ kilometers and it took the plane $t$ hours to fly from Istanbul to Lagos. Thus

\[800 = \frac{d}{t} \mbox{ kilometers per hour.}\]

How long does the return trip take? Write an equation, similar to the one above, for the return trip. Solve the two equation.


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