i Think the concept tested here is that of relative speeds.
Two speeds are added if they move in thesame direction and subtracted if they move in opposite directions.
it is easier to start with Daniel as he moves with a constant speed of 0.5 durint the whole journey which makes his combined speed 1 m/s ( +0.5 of walkway) meaning he moves 200 meters in 200 seconds.
for Carla she running at 1 m/s + 0.5 of the walkway making 1.5 m/s for 40 seconds. applying D = ST formula we see she moved 60 meters durant the first 40 seconds
similarly during the last 5 seconds she was running at 1.5 + 0.5 of the walkway making a combined speed of 2 m/s. D = ST meaning she covered 10 meters during those five seconds.
Distance left for Carla = 200 - (60 + 10) = 130
she covered this 130 standing still ( he speed was only that of the walkway which is 0.5) therefore she covered those 130 meters in 260 seconds.
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.