Final answer:
The scale Sophie used for her drawing is 1:600, which means 1 cm on the drawing represents 6 m in reality.
Step-by-step explanation:
To determine the scale Sophie used for her drawing of a house and its lot, we need to compare the drawing's dimensions to the actual dimensions. Here, the back patio is 3 centimeters (cm) wide in the drawing and 18 meters (m) wide in reality. To find the scale, we divide the actual width by the drawing width:
Scale = Actual width / Drawing width
Scale = 18 m / 3 cm
Since 1 m = 100 cm, we can convert the actual width from meters to centimeters for a more straightforward comparison:
Scale = (18 m * 100 cm/m) / 3 cm
Scale = 1800 cm / 3 cm
Scale = 600
Therefore, the scale Sophie used is 1:600, meaning 1 cm on the drawing represents 600 cm in real life, or equivalently, 1 cm on the drawing represents 6 m in reality.