okay here we are doing permutations and combinations and we've got our cats a b c and d and in this case over here we're going to do a permutation with them so we're taking three of them one's going home with me one's going to my niece's house and one's going to have gumbo made of him and so here i'm going to squeeze on here here are the different possibilities so my my goal is to get the number 24 because this really means how many different ways can i choose out of four three things and over here i have four so that's the difference the combination i'm just going to choose the three cats and put them in my car and take them all and they'll all be my pet so those that's what i'm working from and i want to do these side by side because we're going to compare the formulas so notice i have highlighted here the only difference between these two formulas is this added little extra bit remember these are factorials you can go back to a previous video and check out factorials and how to do them so these are our two formulas so using this formula i'm going to do this is four factorial over 4 minus 3 factorial and i'm going to do these simultaneously so we can see the subtle differences this is 4 factorial over 3 factorial or minus three factorial okay so there's my difference there's the difference let me get rid of my formulas now that i have used them and i have merely the arithmetic to do now so i have four factorial over this is one factorial and one factorial is just one so this is four times three times two times one over one factorial which is one so this is four times three is twelve times two is twenty-four well if i went through and counted these or just looked at them i would notice that there are indeed 24 different permutations doing the calculations here i have four factorial over three factorial one factorial i'm going to put little dickie dudes on that so we can tell the difference this is 4 times 3 factorial over 3 factorial and 1 factorial is just 1 so i'm going to go ahead and stop looking at him i can cancel this and i only have four as my answer so i have four permutations and i have 24 permutations and four combinations and sure enough where's my little here's my four guys versus this amazingly huge thing over here that was the 24. so that's the subtle difference in the actual calculations and the previous video showed how we arrived at these different types of writing out of the letters