Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: Rs.

There are no items in this cart.
Continue Shopping
prakyath p raj Grade: 12

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

8 years ago

Answers : (7)

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

Please feel free to post as many doubts on our discussion forum as you can.
If you find any question Difficult to understand - post it here and we will get you
the answer and detailed  solution very  quickly.

 We are all IITians and here to help you in your IIT JEE preparation.

All the best.
Askiitians Experts

8 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


5 years ago
18 Points




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

4 years ago
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.
4 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}
11 months ago
13 Points
										n^r-nc1(n-1)^r+nc2(n-2)^r-nc3(n-3)^r.....where n=no. of elements in B;r=no. of elements in A.  For a function ,f(A to B).Use this one guys ,its perfectttt.
4 months ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies
  • Complete JEE Main/Advanced Course and Test Series
  • OFFERED PRICE: Rs. 15,900
  • View Details

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details