I spend a lot of time travelling. I consider it 'up' time, not 'down' time, and it is a time within which I always find the time to mess around with a calculator.
Chunking down or breaking down a problem is the easiest way to solve it. Solve the five component parts of a problem and you have solved the BIG problem.
How do you eat an elephant? One bite at a time!
Do you want to make one million pounds or dollars? Then break it down into chunk sized, manageable (do-able) pieces....The result is the same, but the journey becomes more achievable.