Question

Mark the correct alternative in the following question:

If the set A contains 5 elements and the set B contains 6 elements, then the number of one-one and onto mappings from A to B is

(a) 720 (b) 120 (c) 0 (d) none of these

Answer 1

$$\begin{gathered} \mathrm{As},\mathrm{the}\mathrm{number}\mathrm{of}\mathrm{bijection}\mathrm{from}A\mathrm{into}B\mathrm{can}\mathrm{only}\mathrm{be}\mathrm{possible}\mathrm{when}\mathrm{provided}n\left(A\right)\ge n\left(B\right) \\ \mathrm{But}\mathrm{here}n\left(A\right)<n\left(B\right) \\ \mathrm{So},\mathrm{the}\mathrm{number}\mathrm{of}\mathrm{bijection}\mathrm{i}.\mathrm{e}.\mathrm{one}-\mathrm{one}\mathrm{and}\mathrm{onto}\mathrm{mappings}\mathrm{from}A\mathrm{to}B=0 \end{gathered}$$

Hence, the correct alternative is option (c).