I have a basic permutation question where I need some help in getting to the answer fairly quickly. Also, need to know what's the best approach to attack similar problem
Question: If P(n,3) = 210 , find value of n?
So here is what I am doing: n!/(n-3)! = 210
n x (n-1) x (n-2) = 210
I know the answer should be 7 x 6 x 5, but what's the easiest way to split 210 and get to value of n? More importantly how do you know it's 7,6&5? Any help is appreciated.
Another similar question is -
Question: If P (m+n,4) = 3024 and P(m-n,4) =120, find m & n? How would you attack this problem?
Question: If P(n,3) = 210 , find value of n?
So here is what I am doing: n!/(n-3)! = 210
n x (n-1) x (n-2) = 210
I know the answer should be 7 x 6 x 5, but what's the easiest way to split 210 and get to value of n? More importantly how do you know it's 7,6&5? Any help is appreciated.
Another similar question is -
Question: If P (m+n,4) = 3024 and P(m-n,4) =120, find m & n? How would you attack this problem?
. I am aiming to take the GMAT sometime late this summer or early Fall. I just found this website, it looks very resourceful.
