Malik walked up and back down an empty 18m long escalator at a constant rate. Since the escalator was going up at the time, it took him only 22.5s. Going down took Malik 90 s. Assume the escalator speed is constant.What was Malik's walking speed?sm
Q. Malik walked up and back down an empty 18m long escalator at a constant rate. Since the escalator was going up at the time, it took him only 22.5s. Going down took Malik 90 s. Assume the escalator speed is constant.What was Malik's walking speed?sm
Define variables: Define the variables for Malik's walking speed and the escalator speed.Let's denote Malik's walking speed as vm (in meters per second) and the escalator speed as ve (in meters per second).
Set up equations: Set up the equations based on the given information.When Malik is going up, the escalator's speed adds to his walking speed, so the total speed is vm+ve. It takes him 22.5 seconds to cover the 18 meters, so we have the equation:18=(vm+ve)×22.5When going down, the escalator's speed subtracts from his walking speed, so the total speed is vm−ve. It takes him 90 seconds to cover the same distance, so we have the equation:18=(vm−ve)×90
Solve first equation: Solve the first equation for vm+ve.vm+ve=22.518Calculate the right side of the equation.vm+ve=0.8 m/s
Solve second equation: Solve the second equation for vm−ve.vm−ve=9018Calculate the right side of the equation.vm−ve=0.2 m/s
Add equations: Add the two equations to solve for Malik's walking speed vm.(vm+ve)+(vm−ve)=0.8+0.22vm=1.0Now, divide both sides by 2 to find vm.vm=21.0Calculate the value of vm.vm=0.5 m/s
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