Scale Drawings

Scale drawings: a clear method

A scale drawing represents a real object using a smaller or larger version that keeps the same proportions. The key idea is that every matching length changes by the same scale factor.

1) Identify the scale factor

Read the scale carefully. It may compare drawing to real life, or real life to drawing. Make sure you know which quantity is being multiplied or divided.

2) Match corresponding sides

Only use sides that represent the same part of the figure. If one side is doubled in the drawing, every other side must be doubled as well.

3) Compute the unknown length

• If the drawing is enlarged, multiply by the scale factor.
• If the drawing is reduced, divide by the scale factor.
• Keep units consistent before calculating.

4) Simplify the final answer

If your answer is a fraction or ratio, reduce it to lowest terms. If units are included, write them clearly.

5) Check your result

Compare the new length to the original. The ratio between corresponding sides should match the scale. A quick proportionality check helps catch multiplication/division errors.

When solving, write the proportion or operation carefully, then simplify at the end.