Question

Boris is playing on the mall escalators. One escalator goes up, one goes down, and one is out of service; otherwise, they're all identical. The up and down escalators go at the same speed. You can assume that Boris always runs at the same speed.

Boris can run up the up escalator in 6 seconds. He can run up the down escalator in 30 seconds. How long does it take him to run up the out-of-service escalator? Explain your answer.

Answer 1

I think we use
rate*time = distance

let's say Boris runs at a rate of "x"
and the elevator goes up at a rate of "y"
then based on:
run up the up escalator in 6 seconds
we write
(x+y)*6 = d

and based on
the down escalator in 30 seconds
(x-y)*30 = d

Answer 2

I would solve for x as the next step.
can you do that ?