Question

Set A contains 6 elements and set B contains 3 elements. Number of mappings which can be defined A $\to$ B such that each element of set B has exactly two pre-images is

• A. 540
• B. 270
• C. 90
• D. 360

Answer 1

The correct option is C 90

Required number of mappings $=\frac{6!}{2!2!2!}=90$