P/C

edit: (III) is balls differnt, boxes identical

Q2. There are 6 elements in a set A and 3 elements in a set B. Total no. of onto functions from set A to set B if a particular element of A is always associated with a particular element of B is ___

5 Answers

62
Lokesh Verma ·

I) different ways are 6, 5+1, 4+2, 4+1+1, 3+3, 3+ 2+1, 2+2+2, whihc is 7 ways

II) boxes are different, then the number of ways is 6+30+30+6*5C2+6C2+6*5*4+6*5C3+6C3 ways

(Here, each term corresponds to on in I)
III) Think on similar lines as II

IV) 36

106
Asish Mahapatra ·

nishant sir,

isnt (II) simply x+y+z=6?

How to go about (III)? (had doubt only in that one)

62
Lokesh Verma ·

That is what III is x+y+z = 6

106
Asish Mahapatra ·

nishant sir, perhaps u have missed the edit below the first question.. (II) and (III) in the diag are same.. its the (III) that im stuck with

btw can u check my answers for the other parts?

I = 7
II = 28
IV = 36 ?

62
Lokesh Verma ·

asish.. the thing about 3...
edit: (III) is balls differnt, boxes identical

see the thing there is that you have to look at the 3 containers..

if the boxes are identical, then the only difference is that first take those distributions where you have

6+0+0... no of ways is 1

5+1+0... no of ways is 6

4+2+0 .. no of ways is 6C4 = 15

4+1+1... no of ways is 6C4 x 2 = 30

3+3+0 ... no of ways is 6C3/2 = 10

3+2+1.. no of ways is 6C3 x 3C2 = 60

2+2+2... no of ways is 6C2 x 4C2 x 2C2 / 3! = 15

now add these up.. unless i have missed out some case :)

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