JEE AdvancedMathematicsPermutations and CombinationsMCQ+4 / −1
The total number of ways in which 5 balls of different colours can be distributed among 3 persons so that each person gets at least one ball is
- A75
- B150
- C210
- D243
View written solutionFree
Correct answer: B
- Interpret the problem
We have:
- balls, all of different colours so they are distinct.
- persons, also distinct.
- Each person must get at least one ball.
We need the number of onto distributions of distinct objects among distinct persons.
- Total distributions without restriction
Each of the distinct balls can be given to any one of the persons.
So total number of distributions is
- Subtract distributions where at least one person gets no ball
Let the three persons be .
Define:
- = set of distributions where person gets no ball.
If one specific person gets no ball, then each ball can go to only the remaining persons. Thus,
Since there are persons,
- Add back distributions where two persons get no ball
If two specific persons get no ball, then all balls must go to the remaining one person. So for any pair,
Number of such pairs is . Hence,
There is no case where all three get no ball.
- Apply Inclusion-Exclusion Principle
Required number of distributions:
- Check with options
The correct option is: which is Option B.
- Comparison with stored correct answer
Stored correct answer: B
Our derived answer: B
So they agree.
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