Definition: A scale drawing is a smaller or larger picture of a real object in which all lengths are in the same ratio to the actual lengths.
What is a scale drawing?
It is a drawing, like a map or a floor plan, where distances on paper match real distances by a fixed ratio called the scale.
How do you read a scale?
A scale of 1 inch = 15 feet means each inch on the drawing stands for 15 actual feet. Mathbot’s workshop floor plan shows a wall 4.2 inches long. The real length is 4.2 x 15 = 63 feet.
How do you go the other way?
To draw a 90 foot hallway, divide: 90 / 15 = 6 inches.
What about area?
Areas use the square of the scale. If a drawn room is 2 inches by 3 inches, the real room is 30 feet by 45 feet, with area 1,350 square feet, not 6 x 15 = 90.
How do you write scales?
As a ratio such as 1:50, with no units, meaning every unit on the drawing equals 50 of the same unit in life. Or with units, as 1 cm = 8 m.
What is a common error?
Multiplying when you should divide. A drawing is smaller, so converting a real measurement to the drawing needs division.