A question on combinatorics: if $p + q + r = 10$, find the number of possible combinations where the condition holds true.
62036
Finding the number of non-negative integral solutions of $x + y + z = 10$
134599
How do I do Combinatorics / Counting?
56135
Find all permutations with a condition
15349
Combinatorics riddle: keys and a safe
71534
Combinatorial explanation for why $n^2 = {n \choose 2} + {n+1 \choose 2}$
152333
A problem based on pigeonhole
24588
Proving the combinatorial identity ${n \choose k} = {n-2\choose k-2} + 2{n-2\choose k-1} + {n-2\choose k}$
60416
Finding a permutation, and number of, from powers of the permutation
126367
Let $p$, $q$ be prime numbers such that $n^{3pq} – n$ is a multiple of $3pq$ for all positive integers $n$. Find the least possible value of $p + q$.
77595
Number of solutions of $x_1 + 2x_2 + 3x_3 + \cdots + n x_n = p$
27141
Combinatorics identity question
39349
Find count of all combination of numbers whose sum is x
40343
Solutions of $p!q! = r!$
137652
How many solutions does the equation $n_1 + n_2 + n_3 + n_4 + n_5 = 20$ have in the positive integers if $n_1 < n_2 < n_3 < n_4 < n_5$?
60661
How to solve this combination problem quickly?
37569
Prove that $\binom{n}{r} + \binom{n}{r+1} = \binom{n+1}{r+1} $
55562
Number of total possibilities for an equation