Explanation
Now we remove functions in which all match to one elements only.
3. Number of such elements $$= 1 + 1 + 1= 3$$
(One when all match to 6, one when all match to 7 and one when all match to 8)
For functions in which 2 elements are only matched.
4. $$3[\binom {5} {1} + \binom {5} {2} + \binom {5} {3} + \binom {5} {4}]=90$$
If we select any two numbers from $$6,7$$ and $$8.$$ Possible ways are $$3$$.
Now we distribute these $$5$$ numbers from $$1$$ to $$5$$ in different possible ways between the two numbers.
This is done by $$[\binom {5} {1} + \binom {5} {2} + \binom {5} {3} + \binom {5} {4}]$$.
5. Hence the total onto functions are $$= 243 - ( 3 + 90 ) = 150$$
Please disable the adBlock and continue. Thank you.