KöMaL 2021 K686
Each of the integers 1 to 100 is written on a separate piece of paper. 20 pieces of paper are drawn at random from the 100 pieces. Show that it is always possible to select four out of the 20 such that the sum of two numbers equals the sum of the other two.
Official text KöMaL. Quoted with source.
Solutions
No solution is on olymmath yet. Official and human solutions come first when they arrive. AI solutions come after them, with a label.
Similar problems
These problems have the most words in common with this statement.