Thinking with compound quantities
Wrong Track: You can just look at the speedo.
Wrong Track: Power is all around: you can see it in action.
Right Lines: Make the measurements, then combine your results to get the quantity where appropriate
Combine measures to calculate some quantities
Two or more separate measurements are often combined to work out a quantity. Take care to ensure this is clear. It's best not to cut corners, without sharing that you're doing that cutting.