Mathematics - Probability Question with Solution | TestHub

No.of onto functions from A having 5 elements to set B having 3 elements is 150 we shall now count onto function which satisfy $f^{-1}(x)$ is singleton. We can choose a singleton in ${}^5{C}_1$ ways. The remain 4 elements can be mapped to remaining 2 elements in $2^4-2=1\angle$ ways

$\text{ ∴ }\text{ desired prob }=\frac{\frac{5(14)}{150}}{15}$