4. (10 points) There are some black balls and white balls in a box. If the number of black balls is increased to 5 times the original, the total number of balls will become 2 times the original. If the number of white balls is increased to 5 times the original, the total number of balls will become $\qquad$ times the original.
【Analysis】If the number of black balls is increased to 5 times the original, the total number of balls will become 2 times the original. The number of black balls increases by 4 times, and the total number of balls increases by 1 time, which means 4 times the number of black balls is the total number of balls. Therefore, the number of white balls is 4 - 1 = 3 times the number of black balls; if the number of black balls is considered as 1 portion, the number of white balls is 5 portions, and the total number of balls is 4 portions; when the number of white balls becomes 5 times the original, it increases by 4 times, which is an increase of 3 × 4 = 12 portions. Thus, the total number of balls is 12 + 4 = 16 portions, and dividing 16 portions by the original 4 portions gives the factor by which the total number of balls has increased.

【Solution】Solution: If the number of black balls is considered as 1 portion, then the number of white balls is 3 portions, and the total number of balls is 4 portions; when the number of white balls becomes 5 times the original, it increases by 4 times, which is an increase of 3 × 4 = 12 portions.
$$
(12+4) \div 4=4
$$

A diagram can be drawn as follows:
Answer: The total number of balls will become 4 times the original.
The answer is: 4.