- A
- B
- C
- D
View written solutionFree
Correct answer: D
- Total number of ways
Each of the different balls can go into any of the distinct boxes.
Therefore, total number of possible distributions is
- Favourable cases
We want exactly two boxes to contain exactly and balls.
This means:
- one box has balls,
- another box has balls,
- the remaining balls go into the other two boxes.
Also, since the statement says two of these boxes contain exactly 2 and 3 balls, the remaining two boxes must contain numbers of balls different from and .
- Choose the boxes for 2 and 3 balls
Choose the box that gets balls and the box that gets balls:
- Choose the balls for these boxes
- Choose balls out of for the first chosen box:
- Choose balls out of remaining for the second chosen box:
So far, number of ways:
After this, balls remain to be distributed among the remaining boxes.
- Distribute remaining 5 balls into 2 boxes
Each of the remaining distinct balls can go into either of the remaining boxes, so total distributions:
But we must exclude cases where one of these two boxes also gets exactly or balls.
Possible splits of into two boxes are:
Invalid splits are and , because then the remaining boxes also contain exactly and balls, giving more than the intended pair.
Number of ways corresponding to split or :
Hence valid distributions for remaining balls:
- Total favourable ways
Thus,
Now,
So,
Compute: therefore
- Probability
Since we get
Simplify: and
More directly,
Hence,
- Check with options
This matches Option D:
- Comparison with stored answer
Stored correct answer: D
Our derived answer: D
So the stored answer is correct.
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