subsets of {1,2,3, ...,1441} with 77 elements with sum even
Source: 7th Gulf Math Olympiad 2019 GMO p3
December 31, 2019
combinatoricsSubsetsSumProduct
Problem Statement
Consider the set .
1. Nora counts thoses subsets of having exactly two elements, tbe sum of which is even. Rania counts those subsets of having exactly two elements, the sum of which is odd. Determine the numbers counted by Nora and Rania.
2. Let be the number of subsets of which have at least two elements and the product of the elements is even. Determine the greatest power of which divides .
3. Ahmad counts the subsets of having elements such that in each subset the sum of the elements is even. Bushra counts the subsets of having elements such that in each subset the sum of the elements is odd. Whose number is bigger? Determine the difference between the numbers found by Ahmad and Bushra.