When placing each ball, the probability of putting it in the 1 th box is 1/3, and the probability of putting it in other boxes is 2/3. Therefore, the probability P(k) of finally putting k balls into the 1 th box is

P (k) = c (4，k) x ( 1/3) k x (2/3) (4-k)。 [binomial distribution formula]

Take k = 0, 1, 2, 3 respectively, and get the results of (1), (2), (3) and (4):

( 1)P(k = 0)= 16/8 1；

(2)P(k = 1)= 32/8 1；

(3)P(k = 2)= 24/8 1；

(4) P(k=4) = 8/8 1。

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(5) P(k=4) = 1/8 1。

As a verification, the sum of (1) to (5) is equal to 1.