Answer VerifiedHint: We designate the first box left as B1, the second box from the left as B2 and the third box from the left as B3. We ensure that no box is empty by putting one ball in each of them. We find the number of ways we can rest balls in three boxes. This is a problem based on the permutation and combinations. So we will be using the concept of this. Complete step-by-step answer: Note: We can directly find the answer by using the formula of number of positive integral solution to the equation $ {{x}_{1}}+{{x}_{2}}+...+{{x}_{r}}=n $ which is given by $ {}^{r-1}{{C}_{n-1}}. $ If the balls would not have been identical we would have selected 1 ball out of 5 in $ {}^{5}{{C}_{1}} $ ways , put them in boxes and then arranged them in $ 3! $ ways.
My approach : I listed down the following cases :- Case 1) 5 0 0 --> 5c5 = 1 way Case 2) 4 1 0 --> 5c4 * 1c1 = 5 ways Case 3) 3 2 0 --> 5c3 * 2c2 = 10 ways Case 4) 3 1 1 --> 5c3 * 2c1 * 1c1 = 20 ways Case 5) 2 2 1 --> 5c2 * 3c2 * 1c1= 30 ways by adding all this I get 66 ways in which all possible combinations of selecting distinct objects is taken care of , and I feel that I don't need to arrange it further in boxes as all the boxes are identical According to the solution provided for case 4 (i.e. 3,1,1) they have counted 10 ways and for case 5(i.e. 2,2,1) they have counted 15 ways , which makes their total to 41 can someone let me know where exactly am I going wrong with my approach ? |