On the blueprint of a house, 27 millimeters represents 6 meters. The actual length of the living room is 9 meters.

40.5 mm

Step-by-step explanation:

Use a proportion to find the blueprint's length of the living room.

27 mm is to 6 m as x is to 9 m

27/6 = x/9

6x = 27 * 9

6x = 243

x = 40.5

Answer: 40.5 mm