What is the scale if a house plan shows a wall 3cm long but is actually 3m long?

The scale of the house plan can be calculated by dividing the actual length of the wall by the length shown on the plan. In this case, the actual length is 3 meters and the shown length is 3 centimeters. Therefore, the scale would be 1:100, as 3 meters is equivalent to 300 centimeters. This means that each centimeter on the plan represents 100 centimeters (or 1 meter) in reality.