6. (3 points) There are 10 red, 10 yellow, and 10 white small balls, mixed and placed in a cloth bag. At least how many balls must be drawn at once to ensure that 5 of the balls are of the same color?
6. (3 points) There are 10 red, 10 yellow, and 10 white balls, mixed and placed in a cloth bag. At least $\qquad$ balls must be drawn to ensure that 5 balls are of the same color.

【Solution】Solution: Establish drawers: Consider the red, yellow, and white colors as 3 drawers. Consider the worst-case scenario: Draw 12 balls, with each drawer having 4 balls. At this point, drawing 1 more ball, no matter which drawer it goes into, will result in 5 balls of the same color. Therefore, $12+1=13$ (balls). Answer: At least 13 balls must be drawn to ensure that 5 are of the same color. Hence, the answer is: 13.