What is a rational economic decision, meaning one that makes the most sense?

A rational economic decision is the one in which an individual chooses to invest his time, money, and resources in activities that are going to fetch good returns for him.

Explanation:

In some instances, people knowing full well choose to spend their time and money on things that aren't going to give a worthy output compared to the input. Such people can be called to be at an economic loss. When people instead opt to spend their time and money doing activities that would result in economic gains, it is termed as a rational economic decision.