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### Course: Basic geometry and measurement>Unit 12

Lesson 2: Scale drawings

# Making a scale drawing

An urban planner needs your help in creating a scale drawing. Let's use our knowledge about scale factor, length, and area to assist. Created by Sal Khan.

## Want to join the conversation?

• why would u need to have scaled drawings in real life.
• Or if you have a job that requires you to create a model, such as a scientist, an engineer, or an architect.
• I am confused, isn't the area equal to length times width, why did Sal write it as length times length?
• Because it is a square, the length is the same as the width.
• Is there any tool we can use, like a graph of some sort to help us
• You can use graph paper to help you make scale drawings.
Plot a rectangle on a piece of graph paper at these coordinates:

A(0,0) B(0,2) C(3,2) D(3,0)

Now choose your scale factor. For our example, let's say the scale factor is 4.

To graph the new rectangle, multiply each coordinate by 4 to get:
A(0,0) x 4 = A'(0,0)
B(0,2) x 4 = B'(0,8)
C(3,2) x 4 = C'(12,8)
D(3,0) x 4 = D'(12,0)

You now have a new rectangle that is a scale factor of 4 of the original rectangle.

Try graphing the following triangle on your own:
A(0,0) B(3,2) C(4,0)

Now using a scale factor of 2, graph the new coordinates.

Here is something that is really cool. Did you notice anything about the original points and the new points? Pick any coordinate and it's matching scaled coordinate and draw a line connecting them. If you make the line long enough, all of the lines go through the origin!

Great question and hope this helps <|:)
• How come there's no video for the construct a scale drawing?
• There is a video called "Make a Scale Drawing" that is for constructing scale drawings
(1 vote)
• How do you do this
it is so confusing
• I'm being forced to do this at school so I don't really care what I do here
• XD i just looked at ur bio it seems like u dont like very many ppl LMAO...and have fun at school XD
• Sal uses a pen confirmed -
• Scale factor = Dimension of the new shape ÷ Dimension of the original shape?