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prakyath p raj Grade: 12
        

what is the formula to calculate the no. of onto functions from A to  B

7 years ago

Answers : (6)

Badiuddin askIITians.ismu Expert
147 Points
										

Dear prakyath


If A and B are two sets having m and n elements respectively such that   1≤n≤m  then number of onto function from A to B is


  ∑ (-1)n-r  nCr rm   r vary from 1 to n









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7 years ago
Rehan Vijay Jain
18 Points
										

hey can u tell me that in dis ques what shud i take the value of r


Q:- If A= {1,2,3,4}  B={4,5,6}, then find he no. of onto functions in this case.


pls tell me as fast it is possible


i need the answer of it too..........

5 years ago
Raawi Teza
18 Points
										

No of elements of A = 4


No of elements of B = 3


usint this formula  ∑ (-1)n-r  nCr rm   r vary from 1 to n


{[(-1)^(3-1)]*3C1*1^4} + {[(-1)^(3-2)]*3C2*2^4{ +{ [(-1)^(3-3)]*3C3*3^4}


= 1*3*1 + (-1)*3*16 + 1*1*81


= 3-48+81


=36

4 years ago
namita
18 Points
										

HI


 


For 


set a={a,b,c} and B={m,n}


 


the number of onto functions by your formula is 6


 


where as when i try manually it comes 8


 


according to you what should be the anwer

3 years ago
Abishek
8 Points
										If we calculate manually for number of onto functions from A=3 elements to B=2 elements, it comes out to be 6 as from the formula.

Can anyone explain the formula.
3 years ago
Manas Shukla
13 Points
										If there is set A containing a elements and set B containing b elements, formula to calculate no of onto functions is : {(b to power a)- b}
										
6 months ago
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