How many productive hours per year are lost due to traffic congestion?
How many bicycles are there in America?
How to approach these
Clarify the problem
eg: Is the airplane full of people? Traffic internationally or in America? Does “bicycles” include motorcycles?
Scope the problem to something easier to think about
eg: The weight of a plane could be broken down into the wings, engine, all the seats, etc.
Estimate the subcomponents and then combine it all
Talk through possible errors in your estimation
eg: Depends on the material the plane is made of; people might be making productive use of their time in traffic nowadays; transition to bikesharing services may have reduced individual bike ownership, etc.