A molecular model uses the scale 2.5 cm:0.00001 mm. if the model is 7 cm long, how long is the actual molecule

The scale indicates that 2.5cm/0.00001mm = 1, and due to the multiplicative identity property, you can multiply anything in an equation by one, so you would do (7cm) (0.00001mm/2.5cm) = 0.000028