why can't you have greater than 1 probability (tell with examples).

Answer 1

Short answer: Probability of 1 meaning something is CERTAIN to happen is just convention.

Meaning someone made it up a long time ago and people agreed to stick with it.

Given that we say that

Long Answer:

An event (e.g., that it will rain tomorrow) occurring with probability of 1 means that the event will 100% occur. In other words, the event is CERTAIN to occur.

Now why does 100% mean all (like why does 100% of a pizza mean all of the pizza?)...

Well percent = per-cent = per 100 (like how cents are 1/100 of a dollar). So 100% means 100*(1/100) = 1.

Answer 2

A Probability of 1 is the same as 100% probability, just converted into decimals.

100% probability = 1.000

50% probability = 0.5

25% probability = 0.25

You can never have more than 100% probability that an event will occur, so you can never have a probability greater than 1.0