Bunuel
In a certain mega-shopping mall, Carla and Daniel start from the beginning of a 200-meter-long moving walkway and move in the same direction as the walkway, which travels at a constant speed of 0.5 meters per second.
- Carla starts running at a constant rate of 1 meter per second relative to the walkway, continues running for exactly 40 seconds, and then stops running for x seconds. While not running, Carla stands still and is carried only by the walkway.
- Afterward, she resumes running at 1.5 meters per second relative to the walkway for exactly 5 seconds, at which point she reaches the end of the walkway.
- Daniel walks at a constant rate of 0.5 meter per second relative to the walkway, from start to finish without stopping, and reaches the end in y seconds.
Select for
x and
y the value of of x and y, that are consistent with the information provided. Make only two selections, one in each column.
GMAT Club Official Explanation:
The walkway moves at a constant speed of 0.5 meters per second.
Step 1: Distance Carla runs in each phase– In the first phase, Carla runs at 1 meter per second relative to the walkway.
Her total speed = 1 + 0.5 = 1.5 meters per second
Time = 40 seconds
Distance = 1.5 * 40 = 60 meters
– In the last phase, Carla runs at 1.5 meters per second relative to the walkway.
Her total speed = 1.5 + 0.5 = 2.0 meters per second
Time = 5 seconds
Distance = 2.0 * 5 = 10 meters
Step 2: Distance and time while Carla is stationaryTotal distance = 200 meters
Distance already covered while running = 60 + 10 = 70 meters
Remaining distance = 200 - 70 = 130 meters
While standing still, she moves only with the walkway:
Speed = 0.5 meters per second
Time = 130 / 0.5 = 260 seconds
Step 3: Daniel's total timeDaniel walks at 0.5 meters per second relative to the walkway.
His total speed = 0.5 + 0.5 = 1.0 meter per second
Distance = 200 meters
Time = 200 / 1.0 = 200 seconds
Final Answers:x = 260 seconds
y = 200 seconds