MathDB

There is a set of

50

cards. Each card on both sides is colored in one of three colors — red, blue or white, and for each card its two sides are colored in different colors. The cards were laid out on the table. The card lies beautifully if at least one of two conditions is met: its upper side — red; its underside is blue. It turned out that exactly

25

cards are lying beautifully. Then all the cards were turned over. Now some of the cards are lying beautifully on the table. How many of them can there be? K.A.Sukhov

Problem Statement