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Speed, Time and Distance - January 06, 2004
The GMAT Sample Math question for the day is from the topic Speed, Time and Distance.
Question
Jane covered a distance of 340 miles between city A and city taking a total of 5 hours. If part of the distance was covered at 60 miles per hour speed and the balance at 80 miles per hour speed, how many hours did she travel at 60 miles per hour?
A. 2 hours 30 minutes
B. 3 hours
C. 2 hours
D. 1 hour 45 minutes
E. None of these
The correct choice is (B) and the correct answer is 3 hours.
Explanatory Answer
Let ‘x’ hours be the time for which Jane traveled at 60 miles per hour.
As the total time taken to cover 340 miles is 5 hours, Jane would have traveled (5 – x) hours at 80 miles per hour.
Distance covered at 60 miles per hour = Speed * time = 60 * x = 60x miles
Distance covered at 80 miles per hour = Speed * time = 80 (5 – x) = 400 – 80x miles
Total distance covered = Distance covered at 60 miles per hour + Distance covered at 80 miles per hour.
Therefore, total distance = 60x + 400 – 80x.
But, we know that the total distance = 340 miles.
Therefore, 340 = 60x + 400 – 80x
=> 20x = 60 or x = 3 hours.
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