Probability 1 Question 7

7. If 12 identical balls are to be placed in 3 different boxes, then the probability that one of the boxes contains excatly 3 balls, is

(2015 Main)

(a) $\frac{55}{3} \frac{2}{3}$

(b) $55 \frac{2}{3}^{10}$

(c) $220 \frac{1}{3}{ }^{12}$

(d) $22 \frac{1}{3}^{11}$

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Answer:

Correct Answer: 7. (a)

Solution:

  1. We have mentioned that boxes are different and one particular box has 3 balls.

Then, number of ways $=\frac{{ }^{12} C _3 \times 2^{9}}{3^{12}}=\frac{55}{3} \quad \frac{2}{3}{ }^{11}$



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