Update README.md

Author: josemoracard

exercises/015-car_route/README.md

@@ -24,6 +24,8 @@ car_route(20, 40)
 
 + You must round up the outcome if you get a float, for example, if it takes you 1.1 days to travel the distance, it must return 2.
 
++ You may need to import the `math` module for this exercise.
+
 + If you don't know how to start solving this assignment, please review the theory for this lesson: https://snakify.org/lessons/integer_float_numbers/
 
 + You may also try step-by-step theory chunks: https://snakify.org/lessons/integer_float_numbers/steps/1/