M23-09

For relative speed, check:
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/0 ... elatively/
https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/0 ... -concepts/

Hope it helps.

I have edited the question and the solution by adding more details to enhance its clarity. I hope it is now easier to understand.

Hi, I am confused in my approach. We know that the wind/speed is constant, therefore if there is no wind the travel time is the midpoint between the two times, which is 1hr and 54m. From this we can ascertain that win adds 6m to the flight, or roughly 5%. This is equal to about 45km, and since the flight takes two hours, the wind speed should equal about 27kmhr. I'm not sure where is the flaw in my reasoning and would appreciate any clarity.­

Additionally, since the answer is 25kmhr, then we can deduce that the distance added was 50km over 2 hours. This results in 950/900 which is a 5.55% increase in distance.

We also know that it took 2 hours rather than 1hr 54m, which is 120/114 = 5.2%. Since speed is constant, these two figures should equal each other. Clearly there is a mismatch happening somewhere.

 

­No, that's incorrect. For instance, covering 100km at 50km/h takes 2 hours (120 minutes), at 75km/h takes 4/3 hours (80 minutes), and at 100km/h takes 1 hour (60 minutes). As you can see, 80 minutes is not the average of 120 and 60.