Math : Grade 9 : Word Problem on Rates

 A pilot flew from airport A to airport B at a rate of 100 km/hr and flew 

back from airport B to airport A at 120 km/hr. The total time it took was 
11 hours. How far is it from airport A to airport B?

Solution

Let's assume, the distance between the airports = d km

Formula : rate = distance / time

airport A to B

        given, rate = 100 km/hr

                  time = t1 (let's assume time take to reach from airport A to B)

                  distance = d

              100 = d/t1   (substitute values in the formula)

airport B to A

   given, rate = 120 km/hr

                  time = t2 (let's assume time take to reach from airport B to A)

                  distance = d

 

                 120 = d/t2  (substitute values in the formula)

also given total time (that is, from airport A to B and airport B to A)= 11 hours

which is      t1+t2 = 11

Hence, the distance between airports = 600 km