Hi All,
This question doesn't actually require that much 'math' to solve, IF you recognize the logic behind what you "need" to know to answer the question.
We're asked for the length of time that it took to travel 5,000km (including 10 stopovers). To answer this question, we need to know the average speed during the 5,000km trip AND we need to know the length of each of the 10 stopovers.
1) The (i^th) stopover lasted (i^2) minutes.
This gives us a pattern for the length of each stopover:
The 1st stopover lasted 1^2 = 1 minute
The 2nd stopover lasted 2^2 = 4 minutes
The 3rd stopover lasted 3^2 = 9 minutes
Etc.
With this information, we can calculate the total amount of time spent on the stopovers, BUT we don't know how long it took to travel the 5,000km.
Fact 1 is INSUFFICIENT
2) The average speed between any two stopovers was 66km/hr.
Using the Distance Formula, we can calculate the travel time for the 5,000km....
D = (R)(T)
5,000 = (66)(T)
5,000/66 = T
With this information, we know how many hours it took to travel the 5,000km, BUT we don't know how long the stopovers were.
Fact 2 is INSUFFICIENT
Combined we know...
The length of the stopovers
The length to travel the 5,000km
So we CAN calculate the total time for everything.
Combined, SUFFICIENT
Final Answer:
GMAT assassins aren't born, they're made,
Rich