vempatichaitu wrote:
in how many ways can we distribute
(1)5 different balls to 3 different baskets
(2)5 identical balls to 3 different baskets
(3)5 different balls to 3 identical baskets
(4)5 identical balls to 3 identical baskets
Lets tackle the easier question first
2) 5 identical balls to 3 different baskets
This falls into the category called Similar -> Different
As it is similar to different, we don't have to do selection as all of them are same. Only arrangement is required.
A + B + C = 5 => 7C2 = 21
(4)5 identical balls to 3 identical baskets
As again 5 identical balls, there is no selection of balls.
S -> S
Lets say 5 balls goes into the 5 1st basket but as baskets are also identical, hence it doesn't matter. - So we can differentiate based on numbers.
5, 0, 0 - 1 way
4, 1, 0 - 1 way
3, 2, 0 - 1 way
3,1,1 - 1 way
2, 2, 1 - 1 way
Hope I have counted all the possibilities - 5 ways.
(3)5 different balls to 3 identical baskets
D -> S
As the balls are different, the selection matters.
5, 0, 0 - can be only 1 way as all the balls are in a basket and baskets are all identical.
4, 1, 0 - 5C4 - 5 ways.
3, 2, 0 - 5C3 - 15 ways
3, 1, 1 - 5C3 * 2C1 = 15 * 2 = 30 ways.
2,2,1 - 5C2 * 3C2 = 15 * 3 = 45 ways.
Again I hope I have covered all the possibilities.
So total number of ways 96 ways.
(1)5 different balls to 3 different baskets
Now this is a biggie. Selection and arrangement both are required.
D-> D
5, 0, 0 -> 5C5 (Selection) * 3C1 (Arrangement) = 3 ways
4, 1, 0 -> 5C4 * 3C1 * 1C1 * 2C1 = 5 * 3 * 2 = 30 ways
3, 2, 0 -> 5C3 * 3C1 * 3C2 * 2C1 = 15 * 3 * 2 = 90 ways
3, 1, 1 -> 5C3 * 3C1 * 2C1 * 2C1 * 1C1 * 1C1 = 15 * 3 * 2 * 2 = 180 ways
2, 2, 1 -> 5C2 * 3C1 * 3C2 * 2C1 * 1C1 * 1C1 = 15 * 3 * 3 * 2 = 270 ways
Hope I have covered all the possibilities again.
573 ways.
Not sure If I have covered all the possibilities. I can bet on you that apart from 1 st one, other cases may not come in GMAT in the near future. This I learnt from CAT prep days.
the answer is going to be 3^5 ways as each ball has an option to go into any of the 3 baskets
and your answer for the case of- 5 different balls to 3 identical baskets needs to be corrected also
5, 0, 0 - can be only 1 way as all the balls are in a basket and baskets are all identical.
4, 1, 0 - 5C4 - 5 ways.
2,2,1 - 5C2 * 3C2 = 15 * 3 = 45 ways /(2!)(as these cases have baskets taking the same no.of balls)