Measuring the distance from the school to the bookstore, the distance from the bookstore to the library is 2 cm and 1 cm respectively.

Then the actual distance between them is 2× 500 = 1000m, 1× 500 = 500m,

So the walking route from the school to the library through the bookstore is:

Go south 15 meters from the school 1000 meters, and then walk 500 meters west to the library.