How to calculate gradient. You would use a topographic map for this, as well as the map scale to calculate distance. Feel free to watch my other videos on Geography's mapping component.
Mapwork calculations, e.g. distance calculation: https://www.youtube.com/playlist?list=PLt71K0lJFElscNEanuSSOMzstkZrxQotA
Mapping playlist: https://www.youtube.com/playlist?list=PLt71K0lJFEluBHCxlYv2tbtAqUSIKZSM8