How many different groups of four can we pick out of 60? We don't care what order we pick them in. We've seen in previous videos that there is a formula here, but it's important to understand the reasoning behind the formula. I'll write the formula here, but then we'll think about what it's actually saying. This is 60 factorial over 60 minus 4 factorial divided also by 4 factorial, or in the denominator, multiplied by 4 factorial. This is the formula right here. What this is really saying, this part right here, 60 factorial divided by 60 minus 4 factorial, that's just 60 times 59 times 58 times 57.