Three principle of Economics relate to real life's examples

People face trade off:

Trade-off is a situation that involves quality or aspect of something in return for gaining another quality or aspect.

Eg: When I was studying 7^th class. I asked my father to buy a car for us. At that time he has two options either he can buy a car or he can invest somewhere for return to meet future needs. My father went 2^nd option that he invested money in Bank. This is people face trade off.

The cost of something is what you give up to get it:

Nothing free comes in this world you need to give up something in order to gain something.

It is similar to opportunity cost.

Eg: Magnus Carlsen who won World weight championship in Chess. He left the school at the age of 6 years and focused on chess, now he is one of the best grand master in chess who has more rating than others. Here the opportunity cost is School which he left.

Rational People thinks art the margin:

A rational decision maker takes actions only if marginal benefit exceeds the marginal cost.

Eg: When I was pursuing plus 2 I liked to buy FZ second hand bike I had 60,000 rs. But the owner of the bike said cost of the bike Is 58,000 rs and it repairs comes around 6,000 rs which comes around 64,000 rs. So I didn’t go for that. Because rational people thinks at the margin.