So it is 5cm to 1m or 5cm to 1000cm
So the scale is the ratio which is 5:1000. this can be reduced to 1:200
10. if the room is 15cm on one side I can say that the ratio to actual size is 15/x. and scale is 1/200 so:
15/x = 1/200
3000 = x is one side
other side:
20/x = 1/200
4000 = x