kidcorpo wrote:A man goes from city A to city B situated 60 kms apart by a boat. His onward journey was with the stream while the return journey was an upstream journey. It took him four and half hours to complete the round trip. If the speed of the stream is 10 km/hr, how long did it take him to complete the onward journey?
a. 3 hours
b. 3.5 hours
c. 2.25 hours
d. 1.5 hours
OA: D
This is clearly not a GMAT question.
First, there's only 4 answer choices; all GMAT questions have 5 answer choices.
Second, to be solvable we must assume that the speed of the boat (not counting the current) is constant. For all we know the driver went at super speed on the way up and really slowly on the way down. On the GMAT, you'll never have to make those assumptions, the question will clearly include all relevant information.
All that said, and assuming that the speed of the boat was constant, we can solve this question in 15 seconds.
Total trip took 4.5 hours.
The river current was running with the boat on the onward journey and against it on the return journey. Therefore, the onward journey will take less time than the return journed.
Since the onward journey is quicker, it will take less than half the time of the entire trip.
4.5/2 = 2.25. Only 1 answer choice is less than 2.25: choose (D).
