Permutation, combination and probability

[jlyw]

After doing so many past year, I found out that questions on permutation and combination and vary a lot, while probability I still can manage to solve easily.
What are the important thing that we need to look after and consider while doing permutation and combination? Is there any tips? I mean, there will sure be a way to identify when to use this and that right? Are there any classification of the ways that we can do these questions? So, please help me. Thanks.

 

[PlanetMaster]

In English we use the word "combination" loosely, without thinking if the order of things is important. In other words:

> "My fruit salad is a combination of apples, grapes and bananas".
> We don't care what order the fruits are in, they could also be "bananas, grapes and apples"
> or "grapes, apples and bananas", its the same fruit salad.

> "The combination to the safe was 472".
> Now we do care about the order. "724" would not work, nor would "247". It has to be exactly 4-7-2.

So, in Mathematics we use more precise language:
>If the order doesn't matter, it is a Combination.
>If the order does matter it is a Permutation.

 

[jlyw]

I know when to use permutation and combination already. Just that there are a lot of different examples of how they are being used DIFFERENTLY. That's the thing i want to find out. Thanks