Question

It takes ten minutes for $5$ eggs, to be hard boiled, how many minutes would $8$ eggs take if boiled together ?

Answer 1

This is a trick question. Do not use unitary method.
As 5 eggs take ten minutes, 1 egg takes 2 minutes and so 8 eggs will take 16 minutes. This argument is flawed.
The correct argument is: If 5 eggs take 10 minutes to be hard bailed, so will 8 eggs or 10 eggs. As they will all take the same time and will be boiled together.