3. There is a pile of red and white balls, the total number of balls does not exceed 50. It is known that the number of red balls is 3 times the number of white balls, so, the maximum number of red balls is $\qquad$.


【Analysis】36
Key Point: Sum, Difference, and Multiple Problems;
Since the number of red balls is 3 times the number of white balls, the total number of balls should be 4 times the number of white balls, which means the total number of balls must be a multiple of 4; the scenario with the maximum number of red balls corresponds to the scenario with the maximum total number of balls, and the largest multiple of 4 not exceeding 50 is 48; therefore, the total number of balls is at most 48, and in this case, the maximum number of red balls is $48 \div 4 \times 3=36$.