Question

In the gift shop of the history of Flight Museum Elisa bought a kit to make a model of a jet airplane. The actual plane is 21 feet long with a wingspan of 17.5 ft. If the Finish model will be 12 in Long what will the wingspan be?

Answer 1

Assuming the model has a consistent scale, the applicable proportion is
  wingspan/(actual wing) = length/(actual length)
  wingspan/(17.5 ft) = (12 in)/(21 ft)
  wingspan = (17.5 ft)/(21 ft)*(12 in) = 10 in

The model's wingspan will be 10 inches.