A circular arena is being built. On a scale drawing, the radius of the arena is 8 cm. The radius of the actual arena is 120 m. Calculate the scale of the drawing.
To calculate the scale factor of enlargement from the diagram to the actual arena, both lengths must be in the same units.

On the diagram, radius    = 8 cm.
In real life, radius               = 120 m = 12 000 cm.
Scale factor of enlargement = 12 000 ÷ 8 = 1500.
Therefore the scale of the drawing is 1 : 1500.