Answer
Length of escalator = $15 \sqrt 2$ $\approx 21.21$ feet
Work Step by Step
This is an classic example of 45°–45°–90° triangle in which shorter side is given and length of hypotenuse is to be calculated.
Given vertical distance i.e. shorter side = 15 feet
In a 45°–45°–90° triangle, length of hypotenuse is $\sqrt 2$ times the length of shorter side, Hence-
Length of escalator = $15 \times \sqrt 2$ $\approx 21.21$ feet
