TSD Q15

Cities A and B are in different time zones. A is located 3000 km east of B. The table below describes the schedule of an airline operating non-stop flights between A and B. All the times indicated are local and on the same day.

  Assume that planes cruise at the same speed in both directions.

  However, the effective speed is influenced by a steady wind blowing from east to west at 50 kmph.

  Q: What is the time difference between A and B?

  a. 1 hour 30 minutes

  b. 2 hours

  c. 2 hour 30 minutes

  d. 1 hour

  e. can not be determined

Let the time taken for the flight from A to B to Tab and the time from B to A be Tba.

Let the speed of the plane be S, and the time difference be Td.
Then from the information provided above, the following equations can be formed.
Tab=7-td--------(1)
Tba=4+td----(2)

Sab = S+50 -----(3)

Sba = S-50-----(4)
Since the plane would cover the same distance in a trip from A to B and B to A,

Average Speed, Sav, =[(S+50)+(S-50)]/2 = 2S/2 = S.
Average time, Tav, = [(4+td)+(7-td)] = 11/2 = 5.5hrs.
Sav = S = Average distance Between A and B / Average Time = 3000/5.5 = 545 approximately 550km/hr
By this we can calculate the time difference as 1 hour.

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