a student divides all 30 marbles into 5 boxes, paints a few marbles
Source: VMO 2021 P6 Vietnam National Olympiad
December 26, 2020
combinatoricsColoring
Problem Statement
A student divides all marbles into boxes numbered (after being divided, there may be a box with no marbles).
a) How many ways are there to divide marbles into boxes (are two different ways if there is a box with a different number of marbles)?
b) After dividing, the student paints those marbles by a number of colors (each with the same color, one color can be painted for many marbles), so that there are no marbles in the same box. have the same color and from any boxes it is impossible to choose marbles painted in colors. Prove that for every division, the student must use no less than colors to paint the marbles.
c) Show a division so that with exactly colors the student can paint the marbles that satisfy the conditions in question b).