Fermi problems: estimate or exact?
Estimate big numbers in steps with reference sizes, round for a quick estimate and decide when an exact answer is needed.
- Germany: grade 3
Guide
A Fermi problem asks for a number you cannot look up, for example how many grains of rice fit in a cup. You solve it by splitting it into small steps and using a reference size you know (1 g of rice has about 50 grains, two steps are about 1 m).
An estimate (Überschlag) rounds the numbers first and calculates with the rounded numbers. It is enough when you only need a rough idea. When everybody must have a seat or a bill must be paid, you need the exact result.
In every mission you pick the facts you need, write a number sentence and answer in a full sentence. Then ask yourself: is the result sensible?