Question: on a scale of 1cm to 5km,how many centimetres would you use to represent: 40 km
There are 8 lots of 5km in the distance 40 km.
To keep to your scale,you would then use 8 lots of 1 cm to represent this distance.
Scale length for 40 km is 8*1cm = 8cm
Answer: 40 km to scale would be 8 cm