7 ms·
You can go down or right at any point. To go in bottom-right corner, you need n down steps and n right steps. In how many ways can you arrange n things on type
by gobdovan 3mo ago
You can go down or right at any point. To go in bottom-right corner, you need n down steps and n right steps. In how many ways can you arrange n things on type A and n things of type B? In C(2n, n). The problem is about modeling, once you model it correctly, you get the definition of combinations.
- dhosek 3mo agoC(2n, n) isn’t about permutations, but choosing subsets of a set without order, but as I’ve thought about it, the model here is that there are 2n moves to be made and you need to choose n of them to be down (or right, depending on your preference).